Method for establishing a fronthaul interface, method for performing access for a UE, method and apparatus for performing a handover for a UE, data forwarding method, user equipment and base station

ABSTRACT

The present disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. The present disclosure provides a method for performing access for a UE. In addition, the present disclosure discloses a data forwarding method and a data forwarding equipment, user equipment and base station. By the technical solutions disclosed in the present disclosure, a UE may help a base station to forward data of other UEs.

PRIORITY

This application is a Continuation Application of U.S. patentapplication Ser. No. 16/250,519, filed in the U.S. Patent and TrademarkOffice on Jan. 17, 2019 as a Continuation Application of U.S. patentapplication Ser. No. 16/318,244, filed in the U.S. Patent and TrademarkOffice on Jan. 16, 2019 as a National Phase Entry of PCT InternationalApplication No. PCT/KR2018/005290 which was filed on May 8, 2018, andclaims priority to Chinese Patent Application Nos. 201710313812.5,201710458428.4, and 201810010479.5, which were filed on May 5, 2017,Jun. 16, 2017, and Jan. 5, 2018, respectively, the content of each ofwhich is incorporated herein by reference.

BACKGROUND 1. Field

The present disclosure relates to radio communications, and particularlyto a method for establishing a fronthaul interface, a method forperforming access for a UE, a method and apparatus for performing ahandover for a user equipment (UE), a method for data forwarding in a 5Gcommunication network, a user equipment and a base station.

2. Description of the Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a ‘Beyond 4G Network’ or a‘Post LTE System’. The 5G communication system is considered to beimplemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, soas to accomplish higher data rates. To decrease propagation loss of theradio waves and increase the transmission distance, the beamforming,massive multiple-input multiple-output (MIMO), Full Dimensional MIMO(FD-MIMO), array antenna, an analog beam forming, large scale antennatechniques are discussed in 5G communication systems. In addition, in 5Gcommunication systems, development for system network improvement isunder way based on advanced small cells, cloud Radio Access Networks(RANs), ultra-dense networks, device-to-device (D2D) communication,wireless backhaul, moving network, cooperative communication,Coordinated Multi-Points (CoMP), reception-end interference cancellationand the like. In the 5G system, Hybrid FSK and QAM Modulation (FQAM) andsliding window superposition coding (SWSC) as an advanced codingmodulation (ACM), and filter bank multi carrier (FBMC), non-orthogonalmultiple access (NOMA), and sparse code multiple access (SCMA) as anadvanced access technology have been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof Things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofEverything (IoE), which is a combination of the IoT technology and theBig Data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “Security technology” have been demanded forIoT implementation, a sensor network, a Machine-to-Machine (M2M)communication, Machine Type Communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing Information Technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, Machine Type Communication (MTC), andMachine-to-Machine (M2M) communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RadioAccess Network (RAN) as the above-described Big Data processingtechnology may also be considered to be as an example of convergencebetween the 5G technology and the IoT technology.

Modern mobile communications more and more tend to provide serviceshaving higher mobile bandwidths, less latency, and supporting a largenumber of user equipment. In a 5^(th) generation (5G) network orcommunication system, different network elements fall into differentcategories: User Equipments (UEs), access nodes (gNB), core network (CN)functional entities, or more, according to their tasks.

FIG. 1 shows a schematic diagram of system architecture in a nextgeneration of network or a 5G network or communication system.

In the system architecture, a UE 101 is a terminal device used toreceive data.

A next generation of radio access network (NG-RAN) 102 is a radio accessnetwork, including a base station (a gNB or an eNB that is connected toa 5G core network (5GC)) for providing an interface for the UE to accessa radio network.

An access and mobility management function (AMF) 103 is responsible formanaging UE mobility context and security information.

A user plane function (UPF) 104 is configured to provide functions of auser plane.

A session management function (SMF) 105 is responsible for sessionmanagement.

A data network (DN) 106 includes an operator's services, access to theInternet, services of the third party, and so on.

To support virtualizing network functions and achieve more efficientresource management and scheduling, a gNB in the 5G may be furtherdivided into a central unit (gNB-CU) and a distributed unit (gNB-DU)which are abbreviated as CU and DU in the following. The packet dataconvergence protocol (PDCP) and radio resource control (RRC) functionsare on the CU. The radio link control (RLC), media access control (MAC)and physical layer functions are on the DU. Between the CU and the DU,there is a standard open interface F1. The F1 interface may be dividedinto a control plane (F1-C) and a user plane (F1-U). The transportnetwork layer of the F1-C is based on IP transmission. To transmitsignaling more reliably, a stream control transmission protocol (SCTP)protocol is added above the IP. The application layer protocol of the F1interface is F1AP. The SCTP may provide reliable transmission forapplication layer messages. On the transport layer of the F1-U, is userdatagram protocol/internet protocol (UDP/IP), and a general packet radioservice (GPRS) tunneling protocol user plane (GTP-U) is above theUDP/IP, and used to carry protocol data units (PDUs) on the user plane.

As can be seen from the traditional art that, the architecture of 5G isdifferent from that of long term evolution (LTE), and a base station of5G should support a fronthaul interface. However, there is not yet adetailed solution regarding how to support UE access, call setup, andhandover over an F1 interface.

FIG. 2 is a schematic diagram of another system architecture in a 5Gnetwork or communication system.

A UE is connected to a gNB via an air interface (Uu interface) totransmit and receive data in a Control Plane (CP) and a User Plane (UP).

In a practical scenario, different UEs connected to a same gNB may havedifferent radio channel conditions. Some UEs may have a great channelcondition; and some UEs may have a poor channel condition, the QoS ofthose UEs may be influenced significantly so that the user experiencewill be deteriorated seriously. There is another scenario where, whencongestion occurs in a cell, the normal operation of users may not besatisfied if all users perform communication with a base station.Therefore, some UEs are required to help the base station to forwarddata of other UEs.

SUMMARY OF THE INVENTION

The present invention has been made to address at least the abovementioned problems and/or disadvantages and to provide at least theadvantages described below.

The present disclosure provides several methods for establishing afronthaul interface, methods for performing access for a UE, methods andapparatus for performing a handover and communications for a UE, so asto achieve better intercommunications between a DU and a CU.

In an embodiment, the present disclosure provides a method performed bya central unit (CU) of a base station, the method comprising: receivinga first transfer message including a measurement report associated witha terminal; transmitting, to a target distributed unit (DU) of the basestation, a request message for establishing a context associated withthe terminal in the target DU, based on the first transfer message, therequest message including a first identifier allocated for the terminalby the CU; receiving, from the target DU of the base station, a responsemessage as a response to the request message, the response messageincluding the first identifier allocated for the terminal by the CU anda second identifier allocated for the terminal by the target DU; andtransmitting, to a source DU of the base station, a message includinginformation for stopping data transmission associated with the terminal.

In an embodiment, the present disclosure provides a central unit (CU) ofa base station, comprising: a transceiver and a controller coupled withthe transceiver and configured to: receive, from a source distributedunit (DU) of the base station, a first transfer message including ameasurement report associated with a terminal, transmit, to the targetDU of the base station, a request message for establishing a contextassociated with the terminal in the target DU, based on the firsttransfer message, the request message including a first identifierallocated for the terminal by the CU, receive, from the target DU of thebase station, a response message as a response to the request message,the response message including the first identifier allocated for theterminal by the CU and a second identifier allocated for the terminal bythe target DU, and transmit, to the source DU of the base station, amessage including information for stopping data transmission associatedwith the terminal.

In an embodiment, the present disclosure provides a method performed bya source distributed unit (DU) of a base station, the method comprising:receiving, from a terminal, a measurement report; transmitting, to acentral unit (CU) of the base station, a transfer message including themeasurement report associated with the terminal; receiving, from the CUof the base station, a message including information for stopping datatransmission associated with the terminal; and stopping the datatransmission associated with the terminal based on the information.

In an embodiment, the present disclosure provides a source distributedunit (DU) of a base station, comprising: a transceiver and a controllercoupled with the transceiver and configured to: receive, from aterminal, a measurement report, transmit, to a central unit (CU) of thebase station, a transfer message including the measurement reportassociated with the terminal, receive, from the CU of the base station,a message including information for stopping data transmissionassociated with the terminal, and stop the data transmission associatedwith the terminal based on the information.

In an embodiment, the present disclosure provides a method performed bya target distributed unit (DU) of a base station, the method comprising:receiving, from a central unit (CU) of the base station, a requestmessage for establishing a context associated with a terminal, therequest message including a first identifier allocated for the terminalby the CU; configuring at least one of a signal radio bearer (SRB) or adata radio bearer (DRB) for the terminal based on the request message;transmitting, to the CU of the base station, a response message as aresponse to the request message, the response message including thefirst identifier allocated for the terminal by the CU and a secondidentifier allocated for the terminal by the target DU; receiving, fromthe terminal, a radio resource control (RRC) reconfiguration completemessage; and transmitting, to the CU of the base station, a transfermessage including the RRC reconfiguration complete message.

In an embodiment, the present disclosure provides a target distributedunit (DU) of a base station, comprising a transceiver and a controllercoupled with the transceiver and configured to: receive, from a central(CU) of the base station, a request message for establishing a contextassociated with a terminal, the request message including a firstidentifier allocated for the terminal by the CU, configure at least oneof a signal radio bearer (SRB) or a data radio bearer (DRB) for theterminal based on the request message, transmit, to the CU of the basestation, a response message as a response to the request message, theresponse message including the first identifier allocated for theterminal by the CU and a second identifier allocated for the terminal bythe target DU, receive, from the terminal, a radio resource control(RRC) reconfiguration complete message, and transmit, to the CU of thebase station, a transfer message including the RRC reconfigurationcomplete message.

In the data forwarding method disclosed in the present disclosure, a UEenters an enhanced mode according to an indication from a base station,and then the UE forwards data between the base station and other UEs,thus achieving forwarding of data of other UEs by the UE. When other UEshave a poor channel condition or when congestion occurs in a cell of abase station, it may be well solved by the method of the presentdisclosure. Therefore, the user experience is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more apparent from the following detailed descriptionin conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of system architecture in a 5G network orcommunication system;

FIG. 2 is a schematic diagram of another system architecture in a 5Gnetwork or communication system;

FIG. 3 is a schematic diagram of a first method of establishing afronthaul interface according to the present disclosure;

FIG. 4 is a schematic diagram of a second method of establishing afronthaul interface according to the present disclosure;

FIG. 5 is a schematic diagram of a third method of establishing afronthaul interface according to the present disclosure;

FIG. 6 is a schematic diagram of a method for performing access for a UEaccording to the present disclosure;

FIG. 7 is a schematic diagram of a method for performing a handoverbetween different DUs of a same CU for a UE;

FIG. 8 is a schematic diagram of a method for performing access for a UEthrough different DUs of a same CU FIG. 1 is a schematic diagram of thesystem architecture in a 5G communication system;

FIG. 9 is a schematic diagram of a preferred data forwarding methodaccording to the present disclosure;

FIG. 10 is a schematic diagram of a protocol stack structure B0 for a UEaccording to the present disclosure;

FIG. 11 is a schematic diagram of a protocol stack structure B1 for a UEaccording to the present disclosure;

FIG. 12 is a schematic diagram of a protocol stack structure B2 for a UEaccording to the present disclosure;

FIG. 13 is a schematic diagram of a protocol stack structure B3 for a UEaccording to the present disclosure;

FIG. 14 is a schematic diagram of a protocol stack structure B4 for a UEaccording to the present disclosure;

FIG. 15 is a schematic diagram of a protocol stack structure B5 for a UEaccording to the present disclosure;

FIG. 16 is a schematic diagram of a protocol stack structure B6 for a UEaccording to the present disclosure;

FIG. 17 is a schematic diagram of a protocol stack structure B7 for a UEaccording to the present disclosure;

FIG. 18 is a schematic diagram of a protocol stack structure B8 for a UEaccording to the present disclosure;

FIG. 19 is a schematic diagram of Embodiment 7 of the presentdisclosure;

FIG. 20 is a schematic diagram of Embodiment 9 of the presentdisclosure;

FIG. 21 is a schematic diagram of Embodiment 10 of the presentdisclosure;

FIG. 22 is a schematic diagram of Embodiment 11 of the presentdisclosure;

FIG. 23 is a illustrates a block diagram of a structure of a terminalaccording to embodiments of the present disclosure; and

FIG. 24 illustrates a block diagram of a structure of a base stationaccording to embodiments of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT DISCLOSURE

Hereinafter, embodiments of the present invention are described indetail with reference to the accompanying drawings. Those of ordinaryskill in the art will recognize that various changes and modificationsof the embodiments described herein can be made without departing fromthe scope of the present invention. In addition, descriptions ofwell-known functions and constructions may be omitted for clarity andconciseness. The same reference symbols are used throughout the drawingsto refer to the same or like parts.

To make the objects, technical schemes and advantages of the presentdisclosure clearer, the present disclosure will be described in detailhereinafter with reference to accompanying drawings and embodiments.

The present disclosure provides three methods for establishing afronthaul interface between a DU and a CU, and meanwhile providesmethods for performing access for a UE and methods for performing ahandover for a UE after establishing a fronthaul interface. Therespective methods will be described in detail in the following.

Embodiment 1

A first method for establishing a fronthaul interface according to thepresent disclosure is as shown in FIG. 3 . In the method, it is a DUthat initiates an F1 interface establishment procedure. The method maybe applicable to a situation where an O&M has an interface with a CU andwith the DU, or where the O&M only has an interface with the DU. Themethod for establishing a fronthaul interface includes processing at theDU side and at the CU side, and for description purpose, theestablishing method is described through interactions between the DU andthe CU, and the establishing method includes the following steps:

Step 201, a DU sends an F1 establishment request message to a CU.

An operation and maintenance system (O&M) configures a transport layeraddress of the CU to be connected by the DU to the DU. The O&M alsoconfigures application layer information of the DU to the DU.

The F1 establishment request message may include one or more pieces ofthe following information:

-   -   DU identity.    -   Serving cell information list on the DU. The serving cell        information includes: a cell identity, cell frequency        information, uplink transmission bandwidth information, downlink        transmission bandwidth information, a physical cell identity, a        tracking area identity (TAI) or a tracking area code (TAC), a        list of broadcast public land mobile network (PLMN) identities,        transmission reception point (TRP) information, beam        information, information of a physical channel in the cell,        information of a transport channel in the cell, information of a        logic channel in the cell and/or a cell access layer protocol        (AP) identity used for the F1 interface and allocated by the DU.        The cell identity may be a global cell identity or a cell        identity unique on the DU, or other cell identities received        from the O&M. The cell AP identity allocated by the DU is        configured to establish a cell signaling connection for the F1        interface, used to transmit information related to the cell. The        serving cell information also includes clock information, e.g.,        a system frame number (SFN).    -   DU capability information. The DU capability information        includes DU buffer capability, DU capacity information, antenna        capability, power capability, and/or DU fronthaul interface        capability.    -   Step 202, the CU receives an F1 establishment request message.        The CU stores the received information, and sends an F1        establishment response message to the DU.

If the CU receives the DU capability information, the CU uses the DUcapability information to schedule the UE, e.g., deciding a DU forserving the UE, or deciding load balance between different DUs.

The F1 establishment response message may include one or more pieces ofthe following information:

-   -   CU identity. The CU identity may be an identity of a gNB or may        be a separate CU identity.    -   List of PLMN identities supported by the CU.    -   Cell configuration list. Configuration information of a cell in        the cell configuration list includes: a cell identity,        configuration information of a common channel in the cell,        system information in the cell, scheduling information for        sending the system information and/or a cell AP identity for an        F1 interface allocated by the CU. The cell identity may be a        global cell identity or a cell identity unique on the DU or a        cell identity unique on the CU. The configuration information of        the common channel includes configuration information of a        physical channel, configuration information of a transport        channel, and configuration information of a logic channel. The        system information includes master information blocks (MIBs) and        system information blocks. The CU decides the scheduling        information of the system information according to clock        information of the cell received from the DU. The CU includes        the clock information of the cell (e.g., an SFN) received from        the DU in the system information. The cell AP identity allocated        by the CU is used to establish a cell signaling connection for        the F1 interface, used to transmit information related to the        cell. Herein, if the F1 establishment response message includes        the cell configuration list, then it means that the        establishment of the cell is completed through the F1        establishment procedure.

As described in the foregoing, if the F1 establishment response messageincludes the cell configuration list, it means that the cell in the DUis configured through the F1 establishment procedure, and the cellconfiguration list includes the system information in the cell and thescheduling information for sending the system information, which equalsto sending the system information that needs to be broadcasted in thecell to the DU, so that the DU can work rapidly. As another method ofthe present disclosure, the cell establishment procedure may be anindependent procedure, and in this case, the F1 establishment responsemessage does not contain the cell configuration list. Corresponding tothis method, the following steps are further included:

Step 203, the CU sends a cell establishment request message to the DU.

The cell establishment request message contains information of a cell tobe configured. The information of the cell to be configured may be thesame with the cell configuration information in the step 202, which willnot be elaborated herein.

Step 204, the DU sends a cell establishment response message to the CU.

The cell establishment procedure may be used to configure one cell ormultiple cells. In case of configuring one cell, the messages in thestep 203 and the step 204 are sent through the cell signalingconnection, i.e., the cell establishment request message and the cellestablishment response message containing a cell AP identity allocatedby the DU and a cell AP identity allocated by the CU, and in this case,the cell establishment request message and the cell establishmentresponse message may not need to contain the cell identity.

In this method, through the cell establishment procedure, the systeminformation needs to be broadcasted in the cell is sent to the DU, sothat the DU can send system information as soon as possible after thecell is configured successfully. As another method of the presentdisclosure, the system information may be sent through an independentprocedure. Corresponding to this method, the present method furtherincludes the following step:

Step 205, the CU sends a system information transfer message to the DU.

The system information transfer message includes a cell identity, systeminformation in the cell, and scheduling information for sending thesystem information. The CU determines the scheduling information of thesystem information according to the clock information of the cellreceived from the DU. The CU includes the clock information of the cell,e.g., an SFN, received from the DU in the system information.

The system information transfer procedure may be used to transmit systeminformation of one or more cells. If system information of one cell istransmitted, the message in the step 205 is transmitted through the cellsignaling connection, i.e., the system information transfer messagecontains a cell AP identity allocated by the DU and a cell AP identityallocated by the CU, and in this case, the system information transfermessage may not need to contain the cell identity.

Till then, the description of the first method for establishing an F1interface according to the present disclosure is completed. Through themethod, not only application layer information of the DU and the CU canbe exchanged, so as to reduce the configuration cost of the operator,but also the common resources of the DU and the CU can be rapidlyconfigured after the DU is started up, which makes preparation for theaccess of the UE, and can achieve the object of fast start-up.

Embodiment 2

A second method for establishing a fronthaul interface according to thepresent disclosure is as shown in FIG. 4 . In the method, it is a CUthat initiates an F1 interface establishment procedure. The method maybe applicable to a situation where an O&M has an interface with the CUand with a DU, or where the O&M only has an interface with the CU. Themethod for establishing a fronthaul interface includes processing at theDU side and at the CU side, and for description purpose, theestablishing method is described through interactions between the DU andthe CU, and the establishing method includes the following steps:

Step 301, a CU sends an F1 establishment request message to a DU.

An O&M configures a transport layer address of the DU to be connected bythe CU to the CU. The O&M configures the application layer informationon the CU to the CU. If the O&M only has an interface with the CU, thenthe O&M also configures application layer information of each DU to beconnected by the CU to the CU.

The F1 establishment request message may include one or more pieces ofthe following information:

-   -   CU identity. The CU identity may be an identity of a gNB or may        be a separate CU identity.    -   List of PLMN identities supported by the CU.    -   Serving cell information list on the DU. The serving cell        information includes: a cell identity, cell frequency        information, uplink transfer bandwidth information, downlink        transfer bandwidth information, a physical cell identity, a TAI        or a TAC, a list of broadcasted PLMN identities, TRP        information, beam information, information of a physical channel        in the cell, information of a transport channel in the cell,        information of a logic channel in the cell and/or a cell access        layer AP identity used for the F1 interface allocated by the DU.        The cell identity may be a global cell identity or a cell        identity unique on the DU, or other cell identities received        from the O&M. The cell AP identity allocated by the DU is        configured to establish a cell signaling connection for the F1        interface, used to transmit information related to the cell. The        serving cell information also includes clock information, e.g.,        an SFN. It is to be specified that, when the O&M only has an        interface with the CU, the clock information is needed, and the        O&M configures the configuration information of the DU to the        CU, and sends the configuration information of the DU to a        corresponding DU through the CU.    -   Cell configuration list. Configuration information of a cell in        the cell configuration list includes: a cell identity,        configuration information of a common channel in the cell,        system information in the cell, scheduling information for        sending the system information and/or a cell AP identity for an        F1 interface allocated by the CU. The cell identity may be a        global cell identity or a cell identity unique on the DU or a        cell identity unique on the CU. The configuration information of        the common channel includes configuration information of a        physical channel, configuration information of a transport        channel, and configuration information of a logic channel. The        system information includes master information blocks (MIBs) and        system information blocks. The CU decides the scheduling        information of the system information according to clock        information of the DU cell. The CU includes the clock        information (e.g., an SFN) of the DU cell in the system        information. The cell AP identity allocated by the CU is used to        establish a cell signaling connection for the F1 interface, used        to transmit information related to the transfer cell. Herein, if        the F1 establishment request message includes the cell        configuration list, then it means that the establishment of the        cell is completed during the F1 establishment procedure.

Step 302, the DU receives an F1 establishment request message. The DUstores the F1 establishment request message received. If the DU receivescell configuration information, the DU configures a corresponding cell.The DU sends an F1 establishment response message to the CU.

The F1 establishment response message may contain one or more of thefollowing information:

-   -   DU identity.    -   DU capability information. The DU capability information        includes DU cache capability, DU capacity information, antenna        capability, power information and/or fronthaul interface        capability.    -   Cell configuration information. The cell configuration        information is actually configuration information configured by        the DU for the cell, which may be different from the F1        establishment request message in case of receiving by the CU.

The CU stores the information received. If the CU receives the DUcapability information, the CU uses the DU capability information toschedule the UE, for example, deciding a UE for serving the UE, ordeciding load balance between different UEs. The CU sends an F1establishment response message to the DU.

As described in the foregoing, if the F1 establishment request messageincludes the cell configuration list, then it means that the cell neededby the DU has been configured successfully through the F1 establishmentprocedure, and the cell configuration list includes the systeminformation in the cell and the scheduling information for sending thesystem information, which equals to sending the system information thatneeds to be broadcasted in the cell to the DU, so that the DU can workrapidly. As another method of the present disclosure, the cellestablishment procedure may be an independent procedure, and in thiscase, the F1 establishment request message does not contain the cellconfiguration list. Corresponding to this method, the following stepsare further included:

Step 303, the CU sends a cell establishment request message to the DU.

The cell establishment request message contains information of a cell tobe configured. The information of the cell to be configured is the samewith the cell configuration information in the step 301, and will not beelaborated herein.

Step 304, the DU sends a cell establishment response message to the CU.

In the method, through the cell establishment procedure, the systeminformation needs to be broadcasted in the cell is sent to the DU, sothat the DU can send system information as soon as possible after thecell is configured successfully. As another method of the presentdisclosure, the system information may be sent through an independentprocedure. Corresponding to this method, the present method furtherincludes the following steps:

Step 305, the CU sends a system information transfer message to the DU.

The system information transfer message includes a cell identity, systeminformation in the cell, and scheduling information for sending thesystem information. The CU determines the scheduling information of thesystem information according to the clock information of the DU cell.The CU includes the clock information of the DU cell, e.g., an SFN, inthe system information.

The cell establishment procedure may be used to configure one cell ormultiple cells. If it is used to configure one cell, the messages in thestep 303 and the step 304 are sent through the cell signalingconnection, i.e., the system information transfer message containing acell AP identity allocated by the DU and a cell AP identity allocated bythe CU, and in this case, the system information transfer message maynot need to contain the cell identity.

The system information transfer procedure may be used to send systeminformation of one or more cells. If system information of one cell issent, the message in the step 305 is transmitted through the cellsignaling connection, i.e., the system information transfer messagecontaining the cell AP identity allocated by the DU and the cell APidentity allocated by the CU, and in this case, the system informationtransfer message may not need to contain the cell identity.

Till then, the description of the second method for establishing an F1interface according to the present disclosure is completed. Through themethod, not only application layer information of the DU and the CU canbe exchanged, so as to reduce the configuration cost of the operator,and can work when the O&M only has an interface with the CU, but alsothe public resources of the DU and the CU can be rapidly configuredafter the DU is started up, which makes preparation for the access ofthe UE, and can achieve the object of fast start-up.

Embodiment 3

A third method for establishing a fronthaul interface according to thepresent disclosure is as shown in FIG. 5 . In the method, it is a CUthat triggers an F1 interface establishment procedure. The method may beapplicable to a situation where an O&M has an interface with the CU andwith a DU, or where the O&M only has an interface with the CU. Themethod for establishing a fronthaul interface includes processing at theDU side and at the CU side, and for description purpose, theestablishing method is described through interactions between the DU andthe CU, and the establishing method includes the following steps:

Step 401, the CU sends an F1 establishment required message to the DU.

An O&M configures a transport layer address of the DU to be connected bythe CU to the CU. The O&M configures application layer information ofthe CU to the CU. If the O&M only has an interface with the CU, the O&Malso configures application layer information of each DU to be connectedby the CU to the CU.

The F1 establishment required message may include one or more pieces ofthe following information:

-   -   CU identity. The CU identity may be a gNB identity or a separate        CU identity.    -   List of PLMN identities supported by the CU.    -   Serving cell information list on the DU. The serving cell        information includes: a cell identity, cell frequency        information, uplink transfer bandwidth information, downlink        transfer bandwidth information, a physical cell identity, a TAI        or a TAC, a list of broadcast PLMN identities, TRP information,        beam information, information of a physical channel in the cell,        information of a transport channel in the cell, information of a        logic channel in the cell and/or a cell access layer AP        identifier used for the F1 interface and allocated by the DU.        The cell identifier may be a global cell identity or a cell        identity unique on the DU or a unique cell identity received        from the O&M. The cell AP identifier allocated by the DU is used        to establish a cell signaling connection for the F1 interface,        used to transmit information related to the cell. The serving        cell information may also include clock information, such as a        system frame number (SFN). It is to be specified that, when the        O&M only has an interface with the CU, the clock information is        contained, and the O&M configures the configuration information        of the DU to the CU, and passes the configuration information of        the DU to the corresponding DU through the CU.

Step 402, the DU sends an F1 establishment request message to the CU.The DU is configured with the application layer information on the DUthrough the O&M or the DU contains the application layer information onthe DU through the CU.

The F1 establishment request message may include one or more pieces ofthe following information:

-   -   CU identity.    -   Serving cell information list on the DU. The serving cell        information includes: a cell identity, cell frequency        information, uplink transfer bandwidth information, downlink        transfer bandwidth information, a physical cell identity, a TAI        or a TAC, a list of broadcasted PLMN identities, TRP        information, beam information, information of a physical channel        in the cell, information of a transport channel in the cell,        information of a logic channel in the cell and/or a cell access        layer AP identity used for the F1 interface allocated by the DU.        The cell identity may be a global cell identity or a cell        identity unique on the DU, or other cell identities received        from the O&M. The cell AP identity allocated by the DU is        configured to establish a cell signaling connection for the F1        interface, used to transmit information related to the cell. The        serving cell information also includes clock information, e.g.,        an SFN.

Corresponding to the DU obtaining the application layer information fromthe CU, that is to say, if the F1 establishment required message in thestep 401 contains the serving cell information list on the DU, then inthis step, the serving cell information list on the DU does not need tobe contained.

-   -   DU capability information. The DU capability information        includes DU buffer capability, DU capacity information, antenna        capability, power information and/or DU fronthaul interface        capability.

Step 403, the CU receives an F1 establishment request message. The CUstores the received information. If the CU receives the DU capabilityinformation, the CU uses the DU capability information to schedule theUE, e.g., deciding a DU for serving the UE or deciding load balancebetween different DUs. The CU sends an F1 establishment response messageto the DU.

The F1 establishment response message may include one or more pieces ofthe following information:

-   -   List of PLMN identities supported by the CU.    -   Cell configuration list. Configuration information of a cell in        the cell configuration list includes: a cell identity,        configuration information of a common channel in the cell,        system information in the cell, scheduling information for        sending the system information and/or a cell AP identity for an        F1 interface allocated by the CU. The cell identity may be a        global cell identity or a cell identity unique on the DU or a        cell identity unique on the CU. The configuration information of        the common channel includes configuration information of a        physical channel, configuration information of a transport        channel, and configuration information of a logic channel. The        system information includes master information blocks (MIBs) and        system information blocks. The CU decides the scheduling        information of the system information according to clock        information of the DU cell. The CU includes the clock        information of the DU cell (e.g., an SFN) in the system        information. The cell AP identity allocated by the CU is used to        establish a cell signaling connection for the F1 interface, used        to transmit information related to the cell. Herein, if the F1        establishment response message includes the cell configuration        list, then it means that the establishment of the cell is        completed during the F1 establishment procedure.

As described in the foregoing, if the F1 establishment response messageincludes the cell configuration list, it means that the cell needed bythe DU has been configured successfully through the F1 establishmentprocedure, and the cell configuration list includes the systeminformation in the cell and the scheduling information for sending thesystem information, which equals to sending the system information thatneeds to be broadcasted in the cell to the DU, so that the DU can workrapidly. Or, as another method of the present disclosure, the cellestablishment procedure may be an independent procedure, and in thiscase, the F1 establishment response message does not contain the cellconfiguration list. A detailed procedure is the same as that in steps203 and 204, and will not be elaborated herein.

In this method, through the cell establishment procedure, the systeminformation needs to be broadcasted in the cell is sent to the DU, sothat the DU can send system information as soon as possible after thecell is configured successfully. As another method of the presentdisclosure, the system information may be sent through an independentprocedure. Corresponding to this method, a detailed step is the same asthe step 205, and will not be elaborated herein.

When the application layer information of the DU, e.g., the capabilityinformation or clock information of the DU, is updated, the DU sends aDU configuration updating message to the CU to notify the CU of theupdated application layer information. The CU stores the receivedupdated application layer information. Alternatively, the CU may sends aDU configuration updating response message to the DU. When the CUreceives the updating information of the DU and determines to update thesystem information, the CU sends a system information updating messageto the DU, the system information updating message includes updatedsystem information and/or scheduling information of the systeminformation. The CU may send the updated system information and/or thescheduling information of the system information to the DU through theDU configuration updating response message.

When the application layer information of the CU, e.g., the list of PLMNsupported by the CU, is updated, the CU sends a CU configurationupdating message to the DU to notify the DU of the updated applicationlayer information. The DU stores the received updated application layerinformation. Alternatively, the DU may send a CU configuration updatingresponse message to the CU.

Embodiment 4

A method for performing access for a UE is as shown in FIG. 6 , and themethod may be used in a scenario of attach, packet data network (PDN)connection establishment, etc.

For the UE and the core network (including an AMF and a UPF), the accessnetwork entity is a gNB. If the gNB is further divided into CU and DUfunction entities, they are transparent to the UE and the core network.Therefore, when the communication procedures between the UE and the gNBis described, what described is RRC procedures between the UE and thegNB; and when the communication procedures between the gNB and the corenetwork, what described is procedures between the gNB and the AMF orbetween the gNB and the UPF. If the gNB is divided into the CU and DUfunction entities, an entity at the gNB side that actually firstreceives an RRC message from the UE is the DU, and the DU sends the RRCmessage to the CU; and an entity at the gNB side that actually firstreceives an NG message from the AMF is the CU. For description purpose,the procedure between the UE and the gNB is described as a procedurebetween the UE and the DU, and the procedure between the gNB and the AMFor between the gNB and the UPF is described as a procedure between theCU and the AMF or between the CU and the UPF, similarly for otherembodiments, which does not affect the main content of the presentdisclosure. The detailed description irrelevant to the presentdisclosure is omitted, e.g., the procedure between the AMF and the SMFand between the AMF and the UPF. The method shown in FIG. 6 includes thefollowing steps:

Step 501, the UE sends an RRC connection request message to the basestation.

Step 502, the DU receives the RRC connection request message from theUE. The DU receives the message from the UE on a common control channel(CCCH), and knows that the UE is in an idle mode or an inactive mode.The DU sends an initial UE message transfer message to the CU.

The initial UE message transfer message is an F1 application layer APmessage. The F1 application layer AP message may include one or moreinformation elements of the following:

-   -   DU UE AP ID allocated for the UE by the DU.    -   cell identity. The cell identity is to indicate a cell, from        which the DU receives the message from the UE. The cell identity        may be a global cell identity or a cell identity unique on the        DU or a cell identity unique on the CU. If the cell identity is        the cell identity unique on the DU, then the initial UE message        transfer message also contains a DU identity.    -   TAI.    -   RRC message received from the UE.    -   C-RNTI allocated for the UE by the DU.

RRC messages between the DU and the CU may be transmitted through acontrol plane (i.e., through an F1 AP message), or an RRC message on asignaling radio bearer SRB0 may be transmitted through the controlplane, and RRC messages on other SRBs are transmitted through the userplane, i.e., through a GPRS tunneling protocol of the user plane(GTP-U).

Corresponding to the approach, in which the RRC message on the SRB0 istransmitted through the control plane, and the RRC messages on the otherSRBs are transmitted through the user plane, the RRC messages on theother SRBs are transmitted through a same user plane tunnel, or for eachSRB, a user plane tunnel is established, and the RRC messages on theother SRBs are transmitted through user plane tunnels separately.Corresponding to the latter method, the allocated channel information inthe following corresponds to each SRB. The present embodiment providesthree approaches to establish a user plane tunnel for transmitting RRCmessages between the DU and the CU.

Approach 1: in step 502, the DU allocates downlink tunnel information,and sends the allocated downlink tunnel information to the CU through aninitial UE message transfer message. In step 503, the CU allocatesuplink tunnel information, and sends the allocated uplink tunnelinformation to the DU through a radio bearer configuration message. Thedownlink tunnel information and the uplink tunnel information includes aTEID and/or a transport layer address.

Approach 2: in step 502, the DU allocates the downlink tunnelinformation, and sends the allocated downlink tunnel information to theCU through the initial UE message transfer message. In step 505, the CUallocates the uplink tunnel information, and sends the allocated uplinktunnel information to the DU through a downlink RRC transfer message.The downlink tunnel information and the uplink tunnel informationincludes the TEID and/or the transport layer address.

Approach 3: in step 503, the CU allocates uplink tunnel information, andsends the allocated uplink tunnel information to the DU through a radiobearer configuration message. In step 504, the DU allocates downlinktunnel information, and sends the allocated downlink tunnel informationto the CU through a radio bearer configuration response message. Thedownlink tunnel information and the uplink tunnel information includesthe TEID and/or the transport layer address.

Step 503, the CU receives the initial UE message transfer message fromthe DU, and according to the RRC message contained in the initial UEmessage transfer message, the CU knows that the RRC message is an RRCconnection request message. The CU allocates a CU UE AP ID on the F1interface for the UE. The CU sends a radio bearer configuration messageto the DU, to request the DU to establish UE context and configure aradio bearer for the UE, and the radio bearer is a configuration of theSRB. The radio bearer configuration message may include one or more ofthe following information elements:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the DU.    -   cell identity of a cell where the UE is located. The cell        identity is a global cell identity or a cell identifier unique        on the DU or a cell identifier unique on the CU.    -   Information of an RB to be configured. The RB contained in the        radio bearer configuration message may be an SRB and/or a DRB.        In this step, the RB to be configured is an SRB.    -   Configuration information of a physical channel.    -   Configuration information of a transport channel    -   Configuration information of a logic channel.    -   Uplink tunnel information. Corresponding to the Approaches 1 and        3 of establishing a user plane tunnel for transmitting RRC        messages between the DU and the CU, the radio bearer        configuration message includes uplink tunnel information        allocated by the CU. The channel information is transmitted for        RRC messages on all other SRBs other than the SRB0. Or for each        SRB, channel information is allocated.

The radio bearer configuration request message may be a UE contextestablishment request or may be named otherwise, which does not affectthe main content of the present disclosure.

Step 504, the DU configures resources. The DU sends a radio bearerconfiguration response message to the CU. The radio bearer configurationresponse message may include one or more of the following:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the DU.    -   RB information configured for the UE. The RB information is        configuration information of an SRB. Corresponding to the        Approach 3 for establishing a user plane tunnel for transmitting        RRC messages between the DU and the CU, the radio bearer        configuration response message includes information of a        downlink tunnel allocated by the DU.    -   C-RNTI allocated for the UE by the DU.

In the method of the present disclosure, the DU may send the C-RNTIallocated for the UE by the DU to the CU through this step or throughthe step 502. When the CU receives the C-RNTI allocated for the UE bythe DU, the CU stores it. In this way, the CU knows the C-RNTI allocatedfor the UE by the DU in the cell, and during the handover procedure,when the CU needs to allocate a C-RNTI for the UE, the CU selects aC-RNTI unallocated in the cell to the UE.

The radio bearer configuration response message may be a UE contextestablishment response or may be named otherwise, which does not affectthe main content of the present disclosure.

Step 505, the CU sends a downlink RRC transfer message to the DU. Thedownlink RRC transfer message includes one or more of the following:

-   -   CU UE AP ID configured for the UE by the CU;    -   DU UE AP ID configured for the UE by the DU;    -   RRC message. The RRC message in the present embodiment is an RRC        connection establishment message. The CU may send a C-RNTI        allocated to the UE to the UE through the RRC message.    -   Information of a logic channel for sending the RRC message.    -   Uplink tunnel information. Corresponding to the second Approach        for establishing a user plane tunnel for transmitting RRC        messages between the DU and the CU, the downlink RRC transfer        message includes uplink tunnel information allocated by the CU.        The uplink tunnel information is transmitted for RRC messages on        other SRBs except for the SRB0. Or, for each SRB, there is one        piece of channel information allocated.

The CU may send the RRC connection establishment message to the DUthrough the message in the step 503. Corresponding to this method, thestep 505 may not be performed.

Step 506, the DU sends the RRC message received to the UE.

Step 507, the UE sends an RRC connection establishment completionmessage to the base station.

Step 508, the DU sends the received RRC message to the CU through thecontrol plane or the user plane. The DU knows that the received RRCmessage is a message, from which UE according to the message receivedfrom the allocated DCCH resource.

Corresponding to the method of sending the received RRC message to theCU through the control plane, the DU sends an uplink RRC transfermessage to the CU. The uplink RRC transfer message may include one ormore pieces of the following information:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the DU.    -   RRC message. In the present embodiment, the RRC message is an        RRC connection establishment completion message.

Corresponding to the method of sending RRC messages on SRBs except forthat on the SRB0 to the CU through the user plane, the DU sends anuplink RRC message to the CU through the GTP-U.

Corresponding to the method of sending RRC messages on SRBs except forthat on the SRB0 through a user plane tunnel, the header of a packet onthe user plane may include SRB information, e.g., an SRB1 or an SRB2. Orthe CU may indirectly know the SRB information in a received RRC messageby analyzing the RRC message.

Corresponding to the method of sending the RRC messages on other SRBsexcept for that on the SRB0, in which each SRB corresponds to one userplane tunnel, the DU selects an established user plane tunnel totransmit the RRC message to the CU according to the SRB in the RRCmessage received.

Step 509, the CU sends an initial UE message to the AMF.

If the AMF needs only to send an NAS message to the UE, but does notneed to establish a session, then the AMF sends a downlink NAS transfermessage to the base station; if it needs to establish a session, thenthe AMF sends the initial context establishment request message of thestep 510 to the base station.

Step 510, the AMF sends an initial UE context establishment requestmessage to the CU.

If the CU receives the downlink NAS transfer message from the AMF, thenthe CU directly performs the subsequent steps, but does not need toperform the RB reconfiguration procedures in steps 511 to 5016.

The CU sends an RRC message downlink NAS transfer message to the DUthrough a control plane or a user plane.

Corresponding to the method of sending the RRC message to the DU throughthe control plane, the CU sends a downlink RRC transfer message to theDU. The downlink RRC transfer message may include one or more pieces ofthe following information:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the DU.    -   RRC message. In the present embodiment, the RRC message is a        downlink NAS transfer message.

Corresponding to the method of sending RRC messages on SRBs except forthat on the SRB0 through the user plane, the CU sends the downlink NAStransfer message to the DU through the GTP-U.

Corresponding to the method of sending RRC messages on SRBs except forthat on the SRB0 through a user plane tunnel, the header of a packet onthe user plane may include SRB information, e.g., an SRB1 or an SRB2.The header of the packet on the user plane may also include informationregarding on which logic channel, the RRC message is transmitted.

Corresponding to the method of sending RRC messages on SRBs except forthat on the SRB0, in which each SRB corresponds to one user planetunnel, the CU sends an RRC message to the DU through a correspondingchannel, and the DU knows on which SRB, the RRC message is sent to theUE according to a channel in the received information.

Step 511, the CU sends a radio bearer reconfiguration request message tothe DU. The radio bearer reconfiguration request message may include oneor more pieces of the following information:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the DU.    -   Information of an RB or RBs to be added. The information of the        RB to be added includes an identity of the RB, configuration        information of a physical channel of the RB, configuration        information of a transport channel of the RB, configuration        information of a logic channel of the RB, information of a QoS        flow or QoS flows mapped on the RB and/or uplink tunnel        information for the RB. The information of the QoS flow mapped        on the RB includes a flow identity of the QoS flow and QoS        information of the QoS flow. The uplink tunnel information        includes a transport layer address and an uplink TEID.    -   Information of an RB or RBs to be reconfigured. The information        of the RB to be reconfigured includes an identity of the RB,        reconfiguration information of a physical channel of the RB,        reconfiguration information of a transport channel of the RB,        reconfiguration information of a logic channel of the RB,        information of a QoS flow or Qos flows to be added to the RB,        information of a QoS flow or Qos flows to be deleted from the RB        and/or information of a QoS flow to be transmitted on the RB.        The information of the QoS flow to be added on the RB includes        an identity of the QoS flow and QoS information of the QoS flow.        The information of the QoS flow to be reconfigured on the RB        includes an identity of the QoS flow and QoS parameters to be        reconfigured. The information of the QoS flow to be deleted from        the RB includes an identity of the QoS flow.    -   Information of an RB or RBs to be deleted. The information of        the RB to be deleted includes an identity of the RB.

The data transfer through the user plane between the DU and the CU maybe that multiple RBs share one GTP-U channel, or that each RB uses oneGTP-U channel.

Step 512, the DU allocates resources. The DU sends a radio bearerreconfiguration response message to the CU. The radio bearerreconfiguration response message may include one or more of thefollowing:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the DU.    -   Configuration information of an RB. The configuration        information of the RB includes an identity of the RB and        downlink tunnel information allocated by the DU. The downlink        tunnel includes a transport layer address and an uplink TEID.

Step 513, the CU sends an RRC message RRC connection reconfiguration tothe DU through the control plane or the user plane.

Corresponding to the method of sending the RRC message to the DU throughthe control plane, the CU sends a downlink RRC transfer message to theDU. The downlink RRC transfer message may include one or more pieces ofthe following information:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the DU.    -   RRC message. The RRC message in the present embodiment is an RRC        connection reconfiguration message.

Corresponding to the method of sending RRC messages on SRBs except forthat on the SRB0 through the user plane, the CU sends the RRC connectionreconfiguration message to the DU through the GTP-U.

Corresponding to the method of sending RRC messages on SRBs except forthat on the SRB0 through a user plane tunnel, the header of a packet onthe user plane may include SRB information, e.g., an SRB1 or an SRB2.The header of the packet on the user plane may also include informationregarding on which logic channel, the RRC message is transmitted.

Corresponding to the method of sending RRC messages on SRBs except forthat on the SRB0, in which each SRB corresponds to one user planetunnel, the CU sends an RRC message to the DU through a correspondingchannel, and the DU knows on which SRB, the RRC message is sent to theUE according to a channel in the received information.

Step 5014, the DU sends the RRC message received from the CU to the UE.

Step 5015, the UE sends an RRC connection reconfiguration completionmessage to the base station.

Step 5016, the DU sends the received RRC message to the CU through thecontrol plane or the user plane. The DU knows that the RRC message is amessage of which UE according to the message received from the DCCHresources allocated.

Corresponding to the method of sending the received RRC message to theCU through the control plane, the DU sends an uplink RRC transfermessage to the CU. The uplink RRC transfer message may include one ormore pieces of the following information:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the DU.    -   RRC message. The RRC message in the present embodiment is an RRC        connection establishment reconfiguration completion message.

Corresponding to the method of sending RRC messages on SRBs except thaton the SRB0 to the CU through the user plane, the DU sends the uplinkRRC message to the CU through the GTP-U.

Corresponding to the method of sending RRC messages on SRBs except forthat on the SRB0 through a user plane tunnel, the header of a packet onthe user plane may include SRB information, e.g., the SRB1 or the SRB2.Or the CU may indirectly know the SRB information of the received RRCmessage by analyzing the RRC message.

Corresponding to the method of sending RRC messages on SRBs except forthat on the SRB0, in which each SRB has one user plane tunnel, the DUselects to perform transfer on which established user plane tunnelaccording to the SRB of the RRC message received.

Till then, the description of the method for performing access for a UEis completed. Through the method, the problem of performing access for aUE is solved when the gNB is divided into a DU and a CU, and the methodmay be applicable to scenarios of Attach, PDU establishment, and so on,to guarantee that the DU and the CU support interconnection andintercommunication between devices of multiple manufacturers.

Embodiment 5

A method for performing a handover between different DUs of a same CU(i.e., a source DU and a target DU access to a same CU) for a UE is asshown in FIG. 7 . Herein the detailed description irrelevant to thepresent disclosure is omitted, e.g., the procedures among an AMF and anSMF and a UPF. The method includes the following steps:

Step 601, the UE sends a measurement report message to a base station.After a DU receives an RRC message from the UE, it sends the RRC messageto a CU through a control plane or a user plane. The method of sendingthe RRC message to the CU through the control plane or the user plane isthe same as what described in step 508 and step S016, and will not beelaborated herein. The DU in the step is a source DU (S-DU).

Step 602, the CU decides to initiate a handover for the UE. A targetcell of the handover is in another DU. The CU decides to perform anormal handover or a make-before-break (MBB) handover. The CU sends aradio bearer configuration message to a target DU (T-DU), to request theT-DU to establish UE context and configure a radio bearer for the UE,and the radio bearer includes configurations of an SRB and a DRB.

The radio bearer configuration message may include one or more pieces ofthe following information:

-   -   CU UE AP ID allocated for the UE by the CU.    -   Context information of the UE on the S-DU. The context        information of the UE on the S-DU includes a cell identity of a        source cell where the UE is located, configuration information        of an RB or RBs of the UE on the source cell, and/or UE        capability information.    -   Identity of a target cell. The identity of the target cell is a        global cell identity of the target cell or a cell identity        unique on the DU or a cell identity unique on the CU.    -   Information of an RB or RBs to be configured by the T-DU. The RB        included in the radio bearer configuration message may be an SRB        and/or a DRB. In the present step, the RB to be configured is        SRB and DRB information.    -   Configuration information of a physical channel.    -   Configuration information of a transport channel.    -   Configuration information of a logic channel.    -   Uplink tunnel information. Corresponding to each DRB, the radio        bearer configuration message includes uplink tunnel information        allocated by the CU. Corresponding to the method of sending RRC        messages on SRBs except for that on the SRB0 through a user        plane tunnel, the radio bearer configuration message includes        uplink tunnel information allocated to the SRBs by the CU, and        the uplink tunnel information may correspond to each SRB, or may        be a tunnel commonly used for transmitting the RRC messages on        SRBs except for that on the SRB0. The uplink tunnel information        includes a transport layer address and a TEID.    -   MBB handover indication. The information may be contained when        the CU decides to perform an MBB handover.

The radio bearer configuration message may be a UE context establishmentrequest or may be named otherwise, which does not affect the maincontent of the present disclosure.

The present disclosure provides two methods of allocating a C-RNTI forthe UE during a handover:

Method 1: The CU allocates a C-RNTI in a target cell where the UE islocated for the UE;

Method 2: The target DU allocates a C-RNTI in a target cell for the UE.

Corresponding to the Method 1 of allocating a C-RNTI for the UE, the CUallocates the C-RNTI of the target cell where the UE is located for theUE. The CU sends the C-RNTI allocated to the target DU through a radiobearer configuration message. When the CU allocates the C-RNTI for theUE, it needs to guarantee the unique of the C-RNTI in the cell. Becausein the UE initial access procedure, it is the DU that allocates a C-RNTIfor the UE, and the DU will send the C-RNTI allocated for the UE to theCU, so that the CU can send the C-RNTI allocated for the UE to the UEthrough an RRC message. After the CU receives the C-RNTI allocated forthe UE by the DU, it stores the C-RNTI, so that the CU can know that theDU has allocated the C-RNTI for the UE in the cell, and if during thehandover procedure, the CU needs to allocate a C-RNTI for the UE, itselects a C-RNTI not allocated in the cell, and allocates it to the UE.

Step 603, the T-DU configures resources. The T-DU sends a radio bearerconfiguration response message to the CU. The radio bearer configurationresponse message may include one or more pieces of the followinginformation:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the T-DU.    -   RB information configured for the UE. The RB information        includes SRB and DRB configuration information. Corresponding to        each DRB, the radio bearer configuration response message        includes information of a downlink tunnel allocated by the T-DU.        Corresponding to the method of transmitting RRC messages on the        other SRBs except for the SRB0 through the user plane, the        message includes downlink tunnel information allocated for the        SRBs by the T-DU, and the downlink tunnel information may        correspond to each SRB, or may be a channel commonly used for        transmitting the RRC messages on SRBs except for that on the        SRB0. The downlink tunnel information includes a transport layer        address and a TEID.

The radio bearer configuration response message may be a UE contextestablishment response, or may be named otherwise, which does not affectthe main content of the present disclosure.

Corresponding to the Method 2 of allocating a C-RNTI for the UE, thetarget DU allocates the C-RNTI for the UE in the target cell where theUE is located. The target DU sends the allocated C-RNTI to the CUthrough a radio bearer configuration response message. When the DUallocates the C-RNTI for the UE, it needs to guarantee the unique of theC-RNTI in the cell.

Corresponding to the Method 1 of allocating a C-RNTI for the UE, thetarget DU stores the C-RNT contained in the radio bearer configurationmessage received. When next the target DU allocates a C-RNTI for theinitially accessed UE, it does not use this C-RNTI. If the C-RNTIcontained in the radio bearer configuration message received by thetarget DU has been allocated to another UE, then the DU processes thissituation according to the following two approaches:

Approach 1: the target DU sends a radio bearer configuration failuremessage to the CU. The radio bearer configuration failure message mayinclude a reason of failure: an invalid C-RNTI. The CU ends theprocedure of handing over the UE to the T-DU.

Approach 2: the target DU allocates another C-RNTI unused to the UE, andsends the new C-RNTI to the CU through a radio bearer configurationresponse message. After the CU receives the new C-RNTI from the DU, theCU modifies the C-RNTI allocated to the UE.

Step 604, the CU sends an RRC connection reconfiguration message to theS-DU through the control plane or the user plane. The CU includes theC-RNTI of the target cell allocated to the UE into the RRC connectionreconfiguration message, and the C-RNTI is allocated by the CU or by thetarget DU. Corresponding to the method of transmitting through thecontrol plane, the CU sends a downlink RRC transfer message to the S-DU.The downlink RRC transfer message may include one or more pieces of thefollowing information.

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the S-DU.    -   RRC message. In the present embodiment, the RRC message is an        RRC connection reconfiguration message.    -   information of a logic channel for transmitting RRC messages.    -   Information for performing a handover between different DUs. If        the S-DU receives the information for performing a handover        between different DUs, it stops transmitting data to the UE, the        S-DU does not receive uplink data from the UE anymore after the        S-DU sends the received RRC message to the UE.    -   MBB handover indication. If the S-DU receives MBB handover        indication information, then after it sends the RRC message        received to the UE, it may continue to transmit data to the UE        and receive uplink data from the UE. After the S-DU receives an        indication of stopping data transmission from the CU, it stops        transmitting downlink data to the UE and/or stopping receiving        data from the UE. Or the S-DU decides when to stop transmitting        data to the UE, e.g., when the S-DU does not receive an uplink        acknowledgment from the UE anymore, the S-DU will stop        transmitting data to the UE.

Corresponding to the method of sending the RRC connectionreconfiguration message to the S-DU through the user plane, the CU sendsthe following information to the S-DU through a separate F1AP message,or includes the following information in a data packet header.

-   -   Information of handover between different DUs. If the S-DU        receives the information of handover between different DUs, it        stops transmitting data to the UE, and does not receive uplink        data from the UE anymore after the S-DU sends the received RRC        message to the UE.    -   MBB handover Indication. If the S-DU receives the MBB handover        indication information, then after it sends the received RRC        message to the UE, it may continue to transmit data to the UE        and receive uplink data from the UE. When the S-DU receives the        indication of stopping data transmission from the CU, it stops        transmitting downlink data to the UE and/or stopping receiving        data from the UE. Or the S-DU decides when to stop transmitting        data to the UE, e.g., when the S-DU does not receive an uplink        acknowledgement from the UE anymore, the S-DU stops transmitting        data to the UE.

Corresponding to the method of sending the RRC connectionreconfiguration message to the S-DU through the user plane, the datapacket header further includes the CU UE AP ID allocated for the UE bythe CU, the DU UE AP ID allocated for the UE by the S-DU and/orinformation of a logic channel for sending RRC messages.

Step 605, the DU sends the RRC message received to the UE.

Corresponding to the method of the CU deciding to use the MBB handover,and the CU deciding when the S-DU stops transmitting the downlink datato the UE or when the S-DU stops communicating with the UE, when the CUdecides that the S-DU stops transmitting the downlink data to the UE orstopping communicating with the UE, the CU sends a data transferstopping indication message to the S-DU. After the S-DU receives thecorresponding data transfer stopping indication message from the CU, itstops communicating with the UE.

The CU may start to transmit data to the T-DU, and the CU transmits datanot acknowledged by the UE and data received from the UPF to the T-DU.The data is a PDCP PDU.

There are two methods for transmitting the data herein:

Method 1: the CU directly sends data that has not been acknowledged bythe UE and that is received from the UPF to the T-DU. The data is PDCPPDU. Data forwarding between the S-DU and the T-DU is not necessary.

Method 2: the CU directly sends data that has not been acknowledged bythe UE and that is received from the UPF to the T-DU. The data is PDCPPDU. To avoid a situation where the target DU repeatedly transmittingsome RLC PDUs that have been successfully transmitted to the UE by thesource DU, the S-DU sends RLC context at the source DU side to the T-DU.Corresponding to PDCP PDUs, a part of which have been successfullytransmitted, the T-DU only transmits RLC PDUs that have not beenreceived by the UE to the UE, and does not need to transmit all the RLCPDUs to the UE, so as to avoid repeatedly transmitting the data.Corresponding to this method, step 605 a and step 605 b should beperformed. This method is applicable to a situation where the T-DU andthe S-DU have a same RB configuration. Alternatively, the S-DU may alsoforward RLC PDUs that have not been acknowledged by the UE to the T-DU.

Step 605 a, the S-DU sends a first RLC context transfer message to theCU. The first RLC context transfer message may include one or morepieces of the following information:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the S-DU.    -   RLC transfer status. The RLC transfer status includes the SN of        the last GTP-U data packet that has been transmitted        successfully, the SN(s) of GTP-U data packets that have not been        transmitted successfully and/or the SN(s) of RLCs that have not        been transmitted successfully.

Step 605 b, the CU sends a second RLC context transfer message to theT-DU. The second RLC context transfer message may include one or morepieces of the following information:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the T-DU.    -   RLC transfer status. The RLC transfer status includes the SN of        the last GTP-U data packet that has been transmitted        successfully, the SN(s) of GTP-U data packets that have not been        transmitted successfully and/or the SN(s) of RLCs that have not        been transmitted successfully.    -   PDCP transmission and receiving status. The PDCP transmission        status includes the SN of the last GTP-U data packet that has        been transmitted successfully, the SN(s) of GTP-U data packets        that have not been transmitted successfully and/or the receiving        status of uplink PDCPs. The DU, according to the feedback from        the UE on the RLC layer, determines that which PDCP data packets        have been received by the UE, and which PDCP data packets have        not been received by the UE, so as to decide the PDCP        transmission and receiving status.

The RLC context transfer may be referred to as PDCP context transfer ormay be named otherwise, which does not affect the main content of thepresent disclosure.

In the method of the present disclosure, only the step 605 a may beperformed, to notify the PDCP transmission and receiving status to theCU, so that the CU knows that is should send which PDCP data packets tothe T-DU.

The step 605 a and the step 605 b are not mandatory steps for thepresent disclosure.

Step 606, the UE is synchronized to the target cell.

Step 607, the UE sends an RRC connection establishment completionmessage to the base station. The T-DU sends the RRC message received tothe CU through the control plane or the user plane. The method for theDU sending the RRC message to the CU is the same as that in the stepS016, and will not be elaborated herein.

Step 608, the CU sends a UE context releasing message to the S-DU. TheUE context releasing message includes the CU UE AP ID allocated for theUE by the CU, and the DU UE AP ID allocated for the UE by the S-DU.

Till then, the description of the method for performing a handoverbetween different DUs for the UE is completed. Through the method, theproblem of performing a handover for the UE is solved when the gNB isdivided into DUs and a CU, which avoid data loss, and guarantees thatthe DUs and the CU support interconnection and intercommunicationbetween devices of multiple manufacturers.

Embodiment 6

A method for performing access for a UE through different DUs of a sameCU (i.e., the UE performing access through a DU-1 and a DU-2, and theDU-1 and the DU-2 access to the same CU) according to the presentdisclosure is as shown in FIG. 8 . Herein the detailed description ofthe steps irrelevant to the present disclosure is omitted, e.g., theprocedures among the AMF and the SMF and the UPF. The method includesthe following steps:

Step 701, the UE sends a measurement report message to a base station.After the DU receives the RRC message from the UE, it sends the RRCmessage received to the CU through a control plane or a user plane. Howto send the RRC message received to the CU through the control plane orthe user plane is the same as those in step 508 and step S016, and willnot be elaborated herein. The DU of the present step is a DU (the DU-1)that serves the UE.

Step 702, according to the measurement report message from the UE, theCU decides to switch a part of bearers of the UE to a cell of the DU-2.The CU decides whether to perform a normal handover or an MBB handover.The CU sends a radio bearer configuration message to the DU-2, torequest the DU-2 to establish UE context and configure a radio bearerfor the UE. The CU decides whether to switch a part of DRBs or all DRBsto the DU-2. If the SRB is also switched to the DU-2, it means that thisis a handover from the DU-1 to the DU-2, and meanwhile, the DRBs areestablished on the DU-2, and this procedure is equal to a combination ofthe handover procedure in FIG. 6 and the procedure of switching a partof or all of DRBs to the DU-2, which will not be elaborated herein. Theradio bearer configuration message may include one or more of thefollowing information elements:

-   -   CU UE AP ID allocated for the UE by the CU.    -   Context information of the UE on the DU-1. The context        information of the UE includes a cell identifier of a DU-1 cell        where the UE is located, RB configuration information of the UE        on the DU-1 cell and/or UE capability information.    -   Identity of a target cell. The identity of the target cell is a        global cell identity or a cell identity unique on the DU or a        cell identity unique on the CU.    -   Information of RBs to be configured on the DU-2.    -   Configuration information of a physical channel.    -   Configuration information of a transport channel.    -   Configuration information of a logic channel.    -   Uplink tunnel information. Corresponding to each DRB, the radio        bearer configuration message includes uplink tunnel information        allocated by the CU. The uplink tunnel information includes a        transport layer address and a TEID.    -   MBB handover indication.

The radio bearer configuration message may be a UE context establishmentrequest or may be named otherwise, which does not affect the maincontent of the present disclosure.

There are two methods of allocating a C-RNTI for the UE:

Method 1: the CU allocates a C-RNTI on the DU-2 cell for the UE;

Method 2: the DU-2 allocates a C-RNTI on the DU-2 cell for the UE.

Corresponding to the Method 1 of allocating a C-RNTI for the UE, the CUallocates a C-RNTI of the DU-2 cell where the UE is located for the UE.The CU sends the C-RNTI allocated to the DU-2 through the radio bearerconfiguration message. When the CU allocates the C-RNTI for the UE, itneeds to guarantee the unique of the C-RNTI in the cell. Because in theUE initial access procedure, it is the DU that allocates a C-RNTI forthe UE, and the DU will send the C-RNTI allocated for the UE to the CU,so that the CU can send the C-RNTI allocated for the UE to the UEthrough an RRC message. After the CU receives the C-RNTI allocated forthe UE by the DU, it stores the C-RNTI, so that the CU can know that theDU has allocated the C-RNTI for the UE in the cell, and if the CU needsto allocate a C-RNTI for the UE, it selects a C-RNTI not allocated inthe cell, and allocates it to the UE.

Step 703, the DU-2 configures resources. The DU-2 sends a radio bearerconfiguration response message to the CU. The radio bearer configurationresponse message may include one or more of the following informationelements:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the DU-2.    -   RB Information configured for the UE. Corresponding to each RB,        the radio bearer configuration response message contains        downlink tunnel information allocated by the DU-2. The downlink        tunnel information includes a transport layer address and a        TEID.

The radio bearer configuration response message may be a UE contextestablishment response message, or may be named otherwise, which doesnot affect the content of the present disclosure.

Corresponding to the Method 2 of allocating a C-RNTI for the UE, theDU-2 allocates a C-RNTI of the DU-2 cell where the UE is located. TheDU-2 sends the C-RNTI allocated to the CU through a radio bearerconfiguration response message. When the DU-2 allocates C-RNTI for theUE, it needs to guarantee the unique of the C-RNTI in the cell.

Corresponding to the Method 1 of allocating a C-RNTI for the UE, theDU-2 stores the C-RNTI contained in the radio bearer configurationmessage received. The DU-2 will not use the C-RNTI when it allocates aC-RNTI for the UE next time. If the C-RNTI included in the radio bearerconfiguration message received by the DU-2 has been allocated to anotherUE, then the DU-2 has two approaches to process this situation:

Approach 1: the DU-2 sends a radio bearer configuration failure messageto the CU. The radio bearer configuration failure message may include areason of failure: an invalid C-RNTI. The CU ends the procedure ofconfiguring the UE to the DU-2.

Approach 2: the DU-2 allocates another C-RNTI unused to the UE, andsends the new C-RNTI to the CU through a radio bearer configurationresponse message. After the CU receives the new C-RNTI from the DU-2, itmodifies the C-RNTI allocated to the UE using the new C-RNTI from theDU-2.

Step 704, the CU sends an RRC connection reconfiguration message to theDU-1 through the control plane or the user plane. The CU includes theC-RNTI in the DU-2 cell allocated for the UE into the RRC connectionreconfiguration message. The C-RNTI is allocated by the CU or by theDU-2. Corresponding to the method of transfer RRC message through thecontrol plane, the CU sends a downlink RRC transfer message to the DU-1.The downlink RRC transfer message may include one or more pieces of thefollowing information:

-   -   CU UE AP ID allocated for the UE by the CU.    -   DU UE AP ID allocated for the UE by the DU-1.    -   RRC message. In the present embodiment, the RRC message is an        RRC connection reconfiguration message.    -   Information of a logic channel for transmitting the RRC message.    -   Information of an RB or RBs to be switched. The information of        the RB to be switched includes an RB identifier, a target DU        identity and/or a target cell identity. For the RB to be        switched, after the DU-1 sends the RRC message received to the        UE, it stops transmitting data to the UE, and does not receive        uplink data from the UE anymore. The CU may send the information        of the RB to be switched to the DU-1 through a separate message.        Corresponding to the method, the message, through which the CU        notifies the DU of the information of the RB to be switched, may        be sent before or after the present step.    -   MBB handover indication. If the DU-1 receives an MBB handover        indication, then after the DU-1 sends the RRC message received        to the UE, it may continue to send data to the UE and receive        uplink data from the UE on the RB to be switched. After the DU-1        receives a data transmission stopping indication from the CU, it        stops transmitting downlink data to the UE and/or stops        receiving data from the UE on the corresponding RB. Or the DU-1        decides when to stop transmitting the data to the UE, e.g., the        DU-1 stopping transmitting data to the UE after it does not        receive uplink acknowledgment from the UE anymore.

Step 705, the DU-1 sends the RRC message received to the UE.

Corresponding to the method of the CU deciding to use the MBB handover,and the CU deciding when the DU-1 to stop transmitting downlink data tothe UE or stop communicating with the UE on the RB to be switched, theCU sends a data transmission stopping message to the DU-1. After theDU-1 receives the corresponding message from the CU, it stopscommunicating with the UE on the RB to be switched.

The CU may start to transmit data to the DU-2 on the RB, to which thehandover is performed, and the CU transmits data that has not beenacknowledged by the UE and that has been received by the UPF to theDU-2. The data is PDCP PDU.

For the RB to be switched, there are two methods of transmitting data asfollows: Method 1, the CU directly transmits data that has not beenacknowledged by the UE and that is received from the UPF to the DU-2.The data is PDCP PDU. The data forwarding between the DU-1 and the DU-2is not necessary.

Method 2, the CU directly transmits data that has not been acknowledgedby the UE and that is received from the UPF to the DU-2. The data isPDCP PDU. To avoid a situation where the DU-2 repeatedly transmits someRLC PDUs that have been successfully transmitted to the UE by the DU-1,the DU-1 sends RLC context at the source side to the DU-2. Correspondingto PDCP PDUs, a part of which have been successfully transmitted, theDU-2 only transmits RLC PDUs that have not been received by the UE tothe UE, and does not need to transmit all the RLC PDUs to the UE, so asto avoid repeatedly transmitting the data. Corresponding to this method,a step similar to step 605 a and step 605 b should be performed, and theDU-1 sends the RLC context to the DU-2 through the CU. The differencebetween the step and the step 605 a and the step 605 b is that the RLCcontext is only intended for an RB to be switched, and the S-DU is theDU-1, and the T-DU is the DU-2, the other parts are same, which will notbe elaborated herein. The method is applicable to a situation where theRB configurations in the DU-1 and the DU-2 are same. Alternatively, theDU-1 may forward RLC PDUs that have not been acknowledged by the UE tothe DU-2. The step 605 a and the step 605 b are not mandatory steps ofthe present disclosure.

Step 706, the UE is synchronized to the target cell.

Step 707, the UE sends an RRC connection establishment completionmessage to the base station. The DU-1 sends the RRC message received tothe CU through the control plane or the user plane. The DU-1 sends theRRC message to the CU through a method same as that in step S016, whichwill not be elaborated herein.

Step 708, the CU sends a radio bearer configuration completionindication message to the DU-2, and sends the RB configurationinformation received from the UE to the DU-2. The RB configurationinformation may only include a delta configuration, i.e., a differencebetween the configuration configured by the DU-2 for the UE, but theactual configuration in the UE. The message may include fullconfigurations of the UE.

Step 709, the CU sends a radio bearer reconfiguration or RB releasingmessage to the DU-1. The radio bearer reconfiguration or RB releasingmessage includes the CU UE AP ID allocated for the UE by the CU, and aDU UE AP ID allocated for the UE by the DU-1. The message includesinformation of an RB to be released, or information of an RB which isswitched to the DU-2 successfully. The RB information includes an RBidentifier.

Step 710, the DU-1 sends a radio bearer re-configuration response or anRB releasing response message to the CU.

Till then, the description of the method for performing access for a UEthrough different DUs of a same CU is completed. Through the method, theproblem of performing access for the UE through different DUs is solvedwhen a gNB is divided into DUs and a CU, which improves the throughputof the UE, avoids data loss on the switched bearers, and guarantees thatthe DUs and the CU support interconnection and intercommunicationbetween devices of multiple manufacturers.

The methods of establishing a fronthaul interface, methods of performingaccess for a UE, and methods for performing a handover for a UE maysolve the communication problem raised when a gNB is divided into DUsand a CU, reduce the configuration cost of the operator, improves thethroughput of the UE, avoids data loss, and guarantees that the DUs andthe CU support interconnection and intercommunication between devices ofmultiple manufacturers.

The present disclosure provides a method for enhancing the function of aUE and achieving data forwarding in a 5G communication network. In thismethod, a UE enters an enhanced mode upon receiving an indication from abase station and forwards data between the base station and other UEs inthe enhanced mode. By this method, a UE having an enhanced function mayprovide a data forwarding function for other UEs. In this way, the QoSof UEs having a poor channel condition is improved and the userexperience is further improved. The UE in the enhanced mode correspondsto the first UE mentioned in the claims, hereinafter referred to asenUE; and other UEs correspond to the second UE mentioned in the claims.

By the method of the present disclosure, data transmission may still bescheduled by the base station, and may also be scheduled by the UEentering the enhanced mode.

Wherein, if data transmission is still scheduled by the base station,the UE entering the enhanced mode (hereinafter referred to as enUE)receives, from the base station, scheduling information ontime-frequency resources of other UEs scheduled by the base station; andforwarding, by the UE, data between the base station and other UEsincludes: by the UE, receiving downlink data sent to other UEs from abase station, processing the downlink data layer by layer by a protocolstack structure corresponding to the UE in the enhanced mode, andforwarding, to the corresponding other UEs, the downlink data on thecorresponding time-frequency resources according to the schedulinginformation on the time-frequency resources of other UEs; and/or by theUE, receiving, uplink data sent to a base station from other UEs oncorresponding time-frequency resources according to the schedulinginformation on the time-frequency resources of other UEs, processing theuplink data layer by layer by a protocol stack structure correspondingto the UE in the enhanced mode, and forwarding the uplink data to thebase station. In this scheduling way, optionally, the base station mayfurther transmit context information and timing information of other UEsto the enUE. In this case, the enUE is required to advance or delaycorresponding time according to the timing information. The timinginformation is time information to be advanced or delayed when the enUEforwards data of other UEs.

If data transmission is scheduled by the UE entering the enhanced mode,the UE entering the enhanced mode transmits scheduling information ontime-frequency resources to other UEs; and forwarding, by the UE, databetween the base station and other UEs includes: by the UE, receivingdownlink data sent to other UEs from a base station, processing thedownlink data layer by layer by a protocol stack structure correspondingto the UE in the enhanced mode, and forwarding, to other UEs, thedownlink data on the corresponding time-frequency resources according tothe scheduling information; and/or by the UE, receiving uplink data sentto a base station from other UEs on corresponding time-frequencyresources according to the scheduling information, processing the uplinkdata layer by layer by a protocol stack structure corresponding to theUE in the enhanced mode, and forwarding the uplink data to the basestation.

Based on the above two scheduling modes, the enUE may form a new celland accept the access of other UEs in this new cell, or may not form anew cell. If the enUE forms a new cell, the enUE needs to receive, fromthe base station, cell configuration information and access informationused by other UEs to access the enUE, and transmit the accessinformation and allow other UEs to access the enUE according to anaccess request from other UEs.

Based on the above description, the technical data forwarding solutionsof the present disclosure may be summarized as the following severalpreferred modes.

1. The enUE forms a new cell and the new cell operates in an independentmode.

Information sent to the enUE by the base station at least includes oneof the following information (the following information is mainlyinformation used by the enUE to serve other UEs):

a protocol stack structure information used in the enhanced mode;

configuration information of each protocol layer in the used protocolstack structure; and

configuration information of the formed new cell, for example, cell ID,operating frequency information, bandwidth information, informationcarried by a broadcast channel, information carried by a synchronizationchannel, configuration information of an access channel used by a userto access the new cell, and more.

Information sent to other UEs by the base station includes:

configuration information of the new cell that other UEs access, forexample, cell ID, operating frequency information, bandwidthinformation, information carried by a broadcast channel, informationcarried by a synchronization channel, configuration information of anaccess channel used by a user to access the new cell, and more.

2. The enUE forms a new cell and the new cell operates in anon-independent mode.

Information sent to the enUE by the base station at least includes oneof the following information (the following information is mainlyinformation used by the enUE to serve other UEs):

a protocol stack structure information used in the enhanced mode;

configuration information of each protocol layer in the used protocolstack structure;

configuration information of the formed new cell, for example, cell ID,operating frequency information, bandwidth information, informationcarried by a broadcast channel, information carried by a synchronizationchannel, configuration information of an access channel used by a userto access the new cell, and more.

Information sent to other UEs by the base station includes:

configuration information of the new cell that other UEs access, forexample, cell ID, operating frequency information, bandwidthinformation, information carried by a broadcast channel, informationcarried by a synchronization channel, configuration information of anaccess channel used by a user to access the new cell, and more.

The difference between the above two modes lies in that, in the firstmode, the enUE transmits access information to the new cell according tothe configuration information of the base station, and in the secondmode, the enUE may not transmit access information to the new cell, orthe enUE transmits only information on the synchronization channel.

3. The enUE does not form a new cell.

Information sent to the enUE by the base station at least includes oneof the following information (the following information is mainlyinformation used by the enUE to serve other UEs):

a protocol stack structure information used in the enhanced mode;

configuration information of each protocol layer in the used protocolstack structure; and

timing indication information for serving other UEs, the indicationinformation being used to indicate the amount of time to be delayed oradvanced when the enUE receives and/or transmits data of other UEs.

The base station is not required to transmit additional information toother UEs. Processing may be performed according to the existing methodsin the prior art.

FIG. 9 is a flowchart of a preferred method according to the presentdisclosure, including the following steps.

Step 901: A UE reports, to a base station, its capability of supportingan enhanced mode.

This step is an optional step. The base station may know a UE'scapability of supporting an enhanced mode in other ways. For example, itis considered that a UE supports the enhanced mode if this UE reportsthe channel state information on one or more carriers between the UE andother surrounding UEs. If a UE supports the enhanced mode, the UE mayfurther report a protocol stack structure information (which will bedescribed in detail below) supported in the enhanced mode. To expressthe protocol stack structure, the following method may be used: aprotocol stack structure is represented by explicit indicationinformation. For example, “1” represents a first structure, “2”represents a second structure, and so on. Alternatively, configurationinformation of each protocol layer in a protocol stack used by the enUEto serve other UEs may be directly given.

Step 902: The base station transmits, to a selected UE, an indication toenter the enhanced mode.

Correspondingly, the base station may also indicate the selected UE toexit the enhanced mode by issuing signaling.

Preferably, the base station may select a UE having a good channelcondition to enter the enhanced mode, in order to forward data between aUE having a poor channel condition and the base station.

Step 903: The UE in the enhanced mode (hereinafter referred to as enUE)acquires scheduling information on time-frequency resources of this UEand/or time-frequency resources of other UEs scheduled by the basestation. The method for acquiring the scheduling information may bebased on a definite signaling between the base station and the UE, orrealized in other ways, for example, the time-frequency resources areconfigured statically.

This step is an optional step. If the UE forms an independent new cellafter entering the enhanced mode or the scheduling of data of other UEsis executed by the enUE, the data may be forwarded between the basestation and other UEs even without the scheduling information of thebase station.

Step 904: The UE in the enhanced mode forwards data between the basestation and other UEs.

Specifically, the UE in the enhanced mode may receive downlink data sentto other UEs from the base station, process the downlink data layer bylayer by a protocol stack structure corresponding to the enUE in theenhanced mode, and forward the downlink data to one or more served UEs;Alternatively, the UE in the enhanced mode may receive uplink data sentto the base station from one or more served UEs, process the uplink datalayer by layer by a protocol stack structure corresponding to the enUEin the enhanced mode, and forward the uplink data to the base station.

In the following description, actions on the base station side will bedescribed by taking gNB as an example.

In the step 902, to configure the enhanced mode of a UE, the gNB needsto provide, to the UE, at least one of the following information a to d:

a. A protocol stack structure information used when serving other UEs(that is, when forwarding data for other UEs)

In addition to a protocol stack used by the UE to transmit and receiveits own data, the protocol stack structure used when the enUE servesother UEs (that is, when the enUE receives downlink data from the gNBand forwards it to other UEs, and/or when the enUE receives uplink datafrom other UEs and forwards it to the gNB) at least includes one of thefollowing structures:

Protocol stack structure B0, including: a Service Data AdaptationProtocol (SDAP) layer, a Radio Resource Control (RRC) layer, a PacketData Convergence Protocol (PDCP) layer, a Radio Link Control (RLC)layer, a Media Access Control (MAC) layer and a PHY layer. For example,a protocol stack used for data transmission in the user plane includesan SDAP layer, a PDCP layer, an RLC layer, an MAC layer and a PHY layer;and a protocol stack used for data transmission in the control planeincludes an RRC layer, a PDCP layer, an RLC layer, an MAC layer and aPHY layer, as shown in FIG. 10 .

Protocol stack structure B1, including: a PDCP layer, an RLC layer, anMAC layer and a PHY layer. For example, a protocol stack used for datatransmission in the user plane includes a PDCP layer, an RLC layer, anMAC layer and a PHY layer; and a protocol stack used for datatransmission in the control plane includes a PDCP layer, an RLC layer,an MAC layer and a PHY layer, as shown in FIG. 11 .

Protocol stack structure B2, including: part of a PDCP layer, an RLClayer, an MAC layer and a PHY layer, as shown in FIG. 12 . In oneembodiment, part of a PDCP layer includes data integrity protection, andother functions of the PDCP layer are on the gNB side.

Protocol stack structure B3, including: an RLC layer, an MAC layer and aPHY layer, as shown in FIG. 13 .

Protocol stack structure B4, including: part of an RLC layer, an MAClayer and a PHY layer, as shown in FIG. 14 . In one embodiment, part ofan RLC layer includes a segmentation function, and other functions ofthe RLC layer are on the gNB side.

Protocol stack structure B5, including: an MAC layer and a PHY layer, asshown in FIG. 15 .

Protocol stack structure B6, including: part of an MAC layer and a PHYlayer, as shown in FIG. 16 . In one embodiment, part of an MAC layerincludes functions having high time delay requirement, for example,HARQ, and other functions of the MAC layer are on the gNB side, forexample, scheduling.

Protocol stack structure B7, including: a PHY layer, as shown in FIG. 17.

Protocol stack structure B8, including: part of a PHY layer, as shown inFIG. 18 . In one embodiment, part of a PHY layer includes iFFT of thedownlink signal and the addition of a cyclic prefix to the downlinksignal, and FFT of the uplink signal and the removal of a cyclic prefix,and other functions of the PHY layer are on the gNB side.

To express the protocol stack structure, the following methods may beused.

Method 1: A protocol stack structure is represented by explicitindication information. For example, “1” represents structure B1, “2”represents structure B2, and so on.

Method 2: Configuration information of each protocol layer in a protocolstack used by the enUE to serve other UEs may be directly given. Forexample, if protocol stack structure B3 is used, the given informationincludes configuration information of the RLC layer, configurationinformation of the MAC layer, and configuration information of the PHYlayer; and if protocol stack structure B4 is used, the given informationincludes part of configuration information of the RLC layer,configuration information of the MAC layer, and configurationinformation of the PHY layer.

b. Information on a plane that the protocol stack structure serves (forexample, the user plane, the control plane, or both the user plane andthe control plane). This information is optional information. If thisinformation is not included, it is indicated that a plane that theprotocol stack structure serves includes the user plane and the controlplane, or that a plane that the protocol stack structure serves is adefault plane.

In addition to the transmission and reception of the own data of theenUE, the protocol stack used by the enUE may be used only for datatransmission of the user plane of other UEs, or only for datatransmission of the control plane of other UEs, or for data transmissionof both the user plane and the control plane of other UEs.

When the enUE serves other UEs, the protocol stack used for datatransmission of the user plane may be different from the protocol stackused for data transmission of the control plane. The protocol stack usedfor data transmission in the control plane and the user plane may be inany one of the above structures B0 to B8.

As an example, during the data transmission of the user plane, theprotocol stack used by the enUE is a protocol stack indicated by B1(including a PDCP layer, an RLC layer, an MAC layer and a PHY layer),and during the data transmission of the control plane, the protocolstack used by the enUE is a protocol stack indicated by B6 (including anMAC layer and a PHY layer).

As another example, during the data transmission in the user plane, theprotocol stack used by the enUE is a protocol stack indicated by B3(including an RLC layer, an MAC layer and a PHY layer), and during thedata transmission in the control plane, the protocol stack used by theenUE is a protocol stack indicated by B1 (including a PDCP layer, an RLClayer, an MAC layer and a PHY layer).

c. a data transmission direction information of a plane that theprotocol stack structure serves (for example, uplink, or downlink, orboth uplink and downlink). This information is optional information. Ifthis information is not included, it is indicated that the datatransmission direction in a plane that the protocol stack structureserves includes uplink and downlink, or that the data transmissiondirection in a plane that the protocol stack structure serves is adefault direction.

In addition to the transmission and reception of the own data of theenUE, the protocol stack used by the enUE may be used for forwarding ofonly a downlink signal of other UEs (the transmission of this downlinksignal may be in only the control plane, in only the user plane, or inboth the user plane and the control plane), or forwarding of only anuplink signal of other UEs (the transmission of this uplink signal maybe only in the control plane, only in the user plane, or both in theuser plane and the control plane).

d. ID information of a user that the enUE serves. This information isoptional information. If this information is not included, it isindicated that the enUE serves users all by the structures indicated bythe above information a, b and c.

In this way, an enUE may serve different users by different protocolstack structures, different protocol stack structures may be configuredfor different enUEs, different protocol stack structures may beconfigured for different planes, and different protocol stack structuresmay be configured for different data transmission directions.

To configure the enhanced mode of an enUE, there are following possibleconfiguration embodiments:

only a is configured;

only a and b are configured, or multiple sets (a1, b1), (a2, b2), . . .are configured;

only a and c are configured, or multiple sets (a1, c1), (a2, c2), . . .are configured;

only a and d are configured, or multiple sets (a1, d1), (a2, d2), . . .are configured;

only a, b and c are configured, or multiple sets (a1, b1, c1), (a2, b2,c2), . . . are configured;

only a, b and d are configured, or multiple sets (a1, b1, d1), (a2, b2,d2), . . . are configured:

only a, c and d are configured, or multiple sets (a1, c1, d1), (a2, c2,d2), . . . are configured; and

a, b, c and d are configured, or multiple sets (a1, b1, c1, d1), (a2,b2, c2, d2), . . . are configured.

Further, the base station may transmit, to a selected UE, configurationinformation related to forwarding of data of other UEs. Theconfiguration information is used to indicate data to be forwarded bythe selected UE, that is, the configuration information is used toindicate which data from the base station, received by the selected UE,is to be forwarded to other UEs, or to indicate which data is datatransmitted from other UEs and to be forwarded to the base station. Thisconfiguration information may be transmitted to the selected UE togetherwith the indication information which is transmitted by the base stationto the selected UE in the step 902, or transmitted to the selected UE byan independent step after the step 902.

For each of other UEs for which data is to be forwarded by the selectedUE, the configuration information at least includes one of the followinginformation:

1) ID information of other UEs to which the data to be forwardedbelongs;

2) indication information of a bearer to which the data to be forwardedbelongs, wherein the indication information may be ID information of abearer, and further, the indication information may indicate that thebearer is a bearer in the control plane or a bearer in the user plane;

3) ID information of a logical channel to which the data to be forwardedbelongs, wherein the logical channel to which the data to be forwardedbelongs is a logical channel used by the selected UE to receive ortransmit the data forwarded by the selected UE; and

4) information on physical resources to which the data to be forwardedbelongs, wherein the physical resources to which the data to beforwarded belongs are physical resources used by the selected UE toreceive or transmit the data forwarded by the selected UE, for example,time resources, frequency resources, spatial resources, ortime-frequency resources.

The following description will be given by several examples.

In a first example, if a UE selected by a base station (UE0) needs toforward data of two other UEs (UE1 and UE2) and the followinginformation is included in the configuration information transmitted tothe UE0: ID of a bearer to which data of the UE1 forwarded by the UE0belongs is 1 and ID of a bearer to which data of the UE2 forwarded bythe UE0 belongs is 2, then:

If a bearer, to which data received by the UE0 from the base stationbelongs, is a bearer 1, the UE0 forwards the data to the UE1;

If a bearer, to which data received by the UE0 from the base stationbelongs, is a bearer 2, the UE0 forwards the data to the UE2;

If data received by the UE0 from other UEs belongs to the bearer 1, thedata belongs to the UE1, and the UE0 needs to forward the data to thebase station; and

If data received by the UE0 from other UEs belongs to the bearer 2, thedata belongs to the UE2, and the UE0 needs to forward the data to thebase station.

In a second example, if a UE selected by a base station (UE0) needs toforward data of two other UEs (UE1 and UE2) and the followinginformation is included in the configuration information transmitted tothe UE0: data of the UE1, which is forwarded by the UE0, belongs to datareceived on a logical channel 1, and data of the UE2, which is forwardedby the UE0, belongs to data received on a logical channel 2, then:

If data received by the UE0 from the base station is transmitted by thelogical channel 1, the UE0 forwards the data to the UE1;

If data received by the UE0 from the base station is transmitted by thelogical channel 2, the UE0 forwards the data to the UE2;

If data received by the UE0 from other UEs is transmitted by the logicalchannel 1, the data belongs to the UE1, and the UE0 needs to forward thedata to the base station; and

If data received by the UE0 from other UEs is transmitted by the logicalchannel 2, the data belongs to the UE2, and the UE0 needs to forward thedata to the base station.

In a third example, if a UE selected by a base station (UE0) needs toforward data of two other UEs (UE1 and UE2) and the followinginformation is included in the configuration information transmitted tothe UE0: data of the UE1, which is forwarded by the UE0, is from atime-frequency resource block 1, and data of the UE2, which is forwardedby the UE0, is from a time-frequency resource block 2, then:

if the UE0 receives, from the time-frequency resource block 1, data fromthe base station, the UE0 forwards the data to the UE1;

if the UE0 receives, from the time-frequency resource block 2, data fromthe base station, the UE0 forwards the data to the UE2;

if the UE0 receives, from the time-frequency resource block 1, data fromother UEs, the data belongs to the UE1, and the UE0 needs to forward thedata to the base station; and

if the UE0 receives, from the time-frequency resource block 2, data fromother UEs, the data belongs to the UE2, and the UE0 needs to forward thedata to the base station.

Upon receiving the configuration information, the selected UE may replythe base station with a configuration response message to confirm thecorrect reception of the configuration information.

The enUE serves other UEs according to the configured protocol stack. Acell supported by the base station is considered as the first cell, anda cell where enUE serves other UEs is considered as the second cell. Thefirst cell and the second cell may be a same cell or different cells.When they are different cells, they may be different cells at a samefrequency or different cells at different frequencies.

The technical solutions of the present disclosure will be furtherdescribed below in details by several preferred embodiments.

Embodiment 7

This embodiment describes a case where the gNB configures an enUE toenter an enhanced mode B0, i.e., configures an enUE to use a protocolstack structure B0, in order to forward data of other UEs.

Hereinafter, a cell supported by the gNB is referred to as the firstcell, and the communication link between a UE and the gNB in the firstcell is referred to as the first link. After a UE becomes an enUE, insome enhanced modes in the present disclosure, the enUE will form a newcell which is referred to as the second cell, and a direct communicationlink between the enUE and other UEs in the second cell is referred to asthe second link. The first cell and the second cell may be at a samefrequency or different frequencies.

The gNB may select, according to information reported by UEs, a UE thatwill become an enUE.

The information reported by UEs at least contains: channel stateinformation in the first link. Optionally, it may contain at least oneof the following information. UE location information, UE movement speedinformation, UE wireless capability information, information oninterference strength of surrounding radio frequency bands, channelstate information on one or more carriers between a UE and other UEs,video/audio information of the surrounding, etc. Wherein, the channelstate information on one or more carriers between a UE and other UEs mayassist the gNB in selecting a UE to enter an enhanced mode.

The gNB may determine, according to the channel state information in thefirst link reported by each UE, a channel condition between each UE andthe gNB, and determine, according to the channel state information on atleast one carrier between each UE and the surrounding other UEs, achannel condition between UEs, so as to select a UE having a goodchannel condition (better than a first set threshold) to enter anenhanced mode and forward data of a UE having a poor channel condition(worse than a second set threshold) by the UE entering the enhancedmode.

For the selected UE, the gNB may indicate the UE to enter an enhancedmode B1 (i.e., indicate the UE to become an enUE) by using an RRCsignaling (for example, RRC RECONFIGURATION) which carries configurationinformation of a UE-enhanced mode. This configuration information mayfurther include configuration information related to forwarding of dataof other UEs. In addition, the configuration information related toforwarding of data of other UEs may be transmitted to the UE by an RRCsignaling different from the above RRC signaling.

In the RRC signaling from the gNB, at least one of the followingconfiguration information should be provided: a duplex mode used by thesecond link (i.e., TDD, FDD, or full duplex), a carrier and a bandwidthused by the second link, a physical cell ID of a cell where the secondlink is located, a maximum transmission power of the enUE in the secondlink, and an operating mode of the second link (i.e., stand-alone ornon-stand-alone). If the second link operates in the stand-alone mode,then in the RRC signaling from the gNB, information carried by thesynchronization channel and broadcast channel for the second link andthe transmission method thereof should also be provided.

The UE executes corresponding configuration and enters an enhanced mode,and may reply with an RRC signaling (for example, RRC RECONFIGURATIONCOMPLETE) to inform the gNB of the successful execution of thisoperation.

After the UE becomes an enUE, it operates in the enhanced mode B0.Preferably, in this case, the second cell operates in a stand-alonemode, and the enUE transmits a synchronization channel, a broadcastchannel or the like necessary for other UEs to access the second celland receives an access request from other UEs. Other UEs are connectedto the enUE by regarding the enUE as the gNB. Preferably, in this case,the second cell operates in a non-stand-alone mode, and the gNB mayprovide auxiliary information for a UE in the first cell to access thesecond cell. The enUE communicates, by using a protocol stack which isused when serving other UEs in the enhanced mode configured by the gNB,with other UEs in the second cell, and communicates, by using its own UEprotocol stack, with the gNB in the first cell. The enUE forwards dataaccording to the configuration information of the enhanced modeconfigured by the gNB. For example, if the following configuration isincluded in the configuration information: the information on a planeserved by a protocol stack used in the UE-enhanced mode includes boththe control plane data and the user plane data and the data direction inthe plane served by the protocol stack used in the UE-enhanced modeincludes the uplink data and the downlink data, then the enUE forwardsthe uplink control plane data and the uplink user plane data from otherUEs to the gNB and also forwards the downlink control plane data and thedownlink user plane data from the gNB, which are intended for other UEs,to other UEs.

the information on a plane served by a protocol stack used in theUE-enhanced mode in the configuration information may include only oneof the control plane data and the user plane data, or the data directionin the plane served by the protocol stack used in the UE-enhanced modemay include only one of the uplink data and the downlink data. Forexample, the information on a plane served by a protocol stack used inthe UE-enhanced mode includes only the user plane data, and other UEsexchange the control plane data with the gNB in other ways, for example,other UEs are directly connected to the gNB.

FIG. 19 is a schematic diagram of Embodiment 7 of the presentdisclosure. A process for processing data in the user plane and aprocess for processing data in the control plane in this embodiment willbe described in detail below with reference to FIG. 19 .

1. Processes for processing data in the user plane

(1) A process for processing downlink data between the gNB and the enUEincludes the following steps.

Step 1: The gNB processes the raw data belonging to the enUEsuccessively by the SDAP, PDCP, RLC, MAC and PHY layers, and thentransmits the data to the enUE via an interface UU. The raw data is datanot yet processed by the protocol stack.

Step 2: The enUE processes the data received from the gNB successivelyby the PHY, MAC, RLC, PDCP and SDAP layers, to obtain the raw databelonging to the enUE.

(2) A process for processing uplink data between the gNB and the enUEincludes the following steps.

Step 1: The enUE processes the raw data successively by the SDAP, PDCP,RLC, MAC and PHY layers, and then transmits the data to the gNB via aninterface UU1.

Step 2: The gNB processes the data received from the enUE successivelyby the PHY, MAC, RLC, PDCP and SDAP layers, to obtain the raw data sentby the enUE.

(3) A process for processing downlink data between the gNB and other UEsincludes the following steps.

Step 1: The gNB processes raw data belonging to other UEs successivelyby the SDAP, PDCP, RLC, MAC and PHY layers, and then transmits the datato the enUE via an interface UU1.

Step 2: The enUE processes, according to the received configurationinformation related to forwarding of data of other UEs, data belongingto other UEs which is received from the gNB successively by the PHY,MAC, RLC, PDCP and SDAP layers, to obtain the data belonging to otherUEs.

Step 3: The enUE processes the data belonging to other UEs obtained inthe step 2 successively by the SDAP, PDCP, RLC, MAC and PHY layers, andthen transmits the data to corresponding other UEs via an interface UU2.

Step 4: The corresponding other UEs process the received datasuccessively by the PHY, MAC, RLC, PDCP and SDAP layers, to obtain theraw data sent to itselves by the gNB.

During this process, raw data belonging to other UEs may not beforwarded to other UEs by the enUE. That is, in the step 1, the gNBprocesses the raw data belonging to other UEs successively by the SDAP,PDCP, RLC, MAC and PHY layers, and then directly transmits the data toother UEs by an interface UU1 or other interfaces; and then, other UEsobtain the data sent to itselves by the gNB according to the step 4.This is just as the process in the above description: the UE-enhancedmode serves only the control plane data of other UEs, not the user planedata of other UEs; Alternatively, the UE-enhanced mode serves only theuplink transmission direction of other UEs, not the downlinktransmission direction of other UEs. The uplink data processing, uplinkcontrol signaling processing or downlink control signaling processingbetween the gNB and other UEs may be implemented in a similar way, andwill not be repeated here.

(4) A process for processing uplink data between the gNB and other UEsincludes the following steps.

Step 1: Other UEs process raw data sent to the gNB successively by theSDAP, PDCP, RLC, MAC and PHY layers, and then transmit the data to theenUE via an interface UU2.

Step 2: The enUE processes, according to the configuration informationrelated to forwarding of data of other UEs received by the enUE, thereceived data sent to the gNB by other UEs successively by the PHY, MAC,RLC, PDCP and SDAP layers, to obtain the data sent to the gNB by otherUEs.

Step 3: The enUE processes the data sent to the gNB by other UEsobtained in the step 2 successively by the SDAP, PDCP, RLC, MAC and PHYlayers, and then transmits the data to the gNB via an interface UU1.

Step 4: The gNB processes the received data successively by the PHY,MAC, RLC, PDCP and SDAP layers, to obtain the raw data sent to the gNBby other UEs.

During this process, the interface UU1 may perform data transmission viaa wired link, or perform data transmission via a wireless link. Theinterface UU2 performs data transmission via a wireless link.

2. Processes for processing data in the control plane

(1) A process for processing a downlink control signaling between thegNB and the enUE includes the following steps.

Step 1: The gNB generates a control signaling belonging to the enUE inan RRC layer.

Step 2: The gNB processes the control signaling generated in the step 1,successively by the PDCP, RLC, MAC and PHY layers, and then transmits itto the enUE via an interface UU1.

Step 3: The enUE processes the signaling received from the gNBsuccessively by the PHY, MAC, RLC, PDCP and RRC layers, to obtain thecontrol signaling belonging to the enUE.

(2) A process for processing an uplink control signaling between the gNBand the enUE includes the following steps.

Step 1: The enUE generates a control signaling belonging to the enUE inan RRC layer.

Step 2: The enUE processes the control signaling generated in the step 1successively by the PDCP, RLC, MAC and PHY layers, and then transmitsthe control signaling to the gNB via an interface UU1.

Step 3: The gNB processes the signaling received from the enUEsuccessively by the PHY, MAC, RLC, PDCP and RRC layers, to obtain thecontrol signaling sent by the enUE.

(3) A process for processing a downlink control signaling between thegNB and other UEs includes the following steps.

Step 1: The gNB generates a control signaling belonging to other UEs inan RRC layer.

Step 2: The gNB processes the control signaling belonging to other UEssuccessively by the PDCP, RLC, MAC and PHY layers, and then transmitsthe control signaling to the enUE via an interface UU1.

Step 3: The enUE processes, according to the configuration informationrelated to forwarding of data of other UEs received by the enUE, thesignaling belonging to other UEs which is received from the gNBsuccessively by the PHY, MAC, RLC, PDCP and RRC layers, to obtain thesignaling belonging to other UEs.

Step 4: The enUE processes the signaling belonging to other UEs obtainedin the step 3 successively by the RRC, PDCP, RLC, MAC and PHY layers,and then transmits the signaling to corresponding other UEs via aninterface UU2.

Step 5: The corresponding other UEs process the received signalingsuccessively by the PHY, MAC, RLC, PDCP and RRC layers, to obtain thecontrol signaling sent to the corresponding other UEs by the gNB.

During this process, the control signaling belonging to other UEs maynot be forwarded to other UEs by the enUE. That is, in the step 2, thegNB processes the control signaling belonging to other UEs successivelyby the PDCP, RLC, MAC and PHY layers, and then directly transmits thecontrol signaling to other UEs by an interface UU1 or other interfaces;and then, other UEs obtain the control signaling sent to other UEs bythe gNB according to the step 5. This is just as the process in theabove description: the UE-enhanced mode serves only the user plane dataof other UEs, not the control plane data of other UEs; Alternatively,the UE-enhanced mode serves only the uplink transmission direction ofother UEs, not the downlink transmission direction of other UEs. Inaddition, the control signaling belonging to other UEs may be generatedby the enUE (that is, it is not required to generate an RRC signalingfor other UEs by the gNB), and then successively processed by the PDCP,RLC, MAC and PHY layers and transmitted to other UEs. Then, the controlsignaling sent to the UEs may be obtained according to the step 5.

(4) A process for processing an uplink control signaling between the gNBand other UEs includes the following steps.

Step 1: Other UEs generate a control signaling in an RRC layer.

Step 2: Other UEs process the control signaling generated in the step 1successively by the PDCP, RLC, MAC and PHY layers, and then transmit thecontrol signaling to the gNB via an interface UU2.

Step 3: The enUE processes, according to the configuration informationrelated to forwarding of data of other UEs received by the enUE, thesignaling received from other UEs successively by the PHY, MAC, RLC,PDCP and RRC layers, to obtain the signaling belonging to other UEs.

Step 4: The enUE processes the signaling belonging to other UEs obtainedin the step 3 successively by the RRC, PDCP, RLC, MAC and PHY layers,and then transmits the signaling to the gNB via an interface UU1.

Step 5: The gNB processes the received data successively by the PHY,MAC, RLC, PDCP and RRC layers, to obtain the control signaling sent byother UEs.

During this process, the control signaling may not be forwarded to thegNB by the enUE. That is, in the step 2, other UEs process the controlsignaling successively by the PDCP, RLC, MAC and PHY layers, and thendirectly transmit the control signaling to the gNB via an interface UU1or other interfaces; and then, the gNB obtains the control signalingsent by other UEs according to the step 5. This is just as the processin the above description: the UE-enhanced mode serves only the userplane data of other UEs, not the control plane data of other UEs;Alternatively, the UE-enhanced mode serves only the downlinktransmission direction of other UEs, not the uplink transmissiondirection of other UEs. In addition, the control signaling sent by otherUEs may be obtained in the following way: a control signaling isgenerated by other UEs, then processed by the PDCP, RLC, MAC and PHYlayers and transmitted to the enUE, and then processed by the PHY, MAC,RLC, PDCP and RRC layers on the enUE side. The enUE is not required totransmit an RRC signaling of other UEs to the gNB.

During this process, the interface UU1 may perform data transmission viaa wired link, or perform data transmission via a wireless link. Theinterface UU2 performs data transmission via a wireless link.

Embodiment 8

This embodiment describes a case where the gNB configures an enUE toenter an enhanced mode B0 in order to forward data of other UEs.

In this embodiment, a cell supported by the gNB is referred to as thefirst cell, and the communication link between a UE and the gNB in thefirst cell is referred to as the first link. After a UE becomes an enUE,the enUE still serve other UEs in the first cell, and a communicationlink used by the enUE to serve other UEs is referred to as the secondlink.

The gNB may select one UE, and indicate the UE to enter an enhanced modeB0 (i.e., indicate the UE to become an enUE) by using an RRC signaling(for example, RRC RECONFIGURATION) which carries configurationinformation of a UE-enhanced mode. The gNB may select a UE that willbecome an enUE according to the information reported by UEs. Theinformation reported by UEs may contain at least one of the followinginformation: channel state information in the first link, locationinformation, movement speed information, UE wireless capabilityinformation, information on interference strength of surrounding radiofrequency bands, channel state information on one or more carriersbetween a UE and other UEs, video/audio information of the surrounding,etc. In the RRC signaling from the gNB, at least one of the followingconfiguration information should be provided: a duplex mode used by thesecond link (i.e., TDD, FDD, or full duplex), a carrier and a bandwidthused by the second link, a maximum transmission power of the enUE in thesecond link, and an operating mode of the second link (i.e., stand-aloneor non-stand-alone). The UE executes this operation and may reply withan RRC signaling (for example, RRC RECONFIGURATION COMPLETE) to notifythe gNB of the successive execution of this step.

After the UE becomes an enUE, it operates in the enhanced mode B0.Preferably, in this case, the second link operates in a stand-alonemode, and the enUE transmits a synchronization channel, a broadcastchannel or the like necessary for other UEs to access the enUE andreceives an access request from other UEs. Other UEs are connected tothe enUE by regarding the enUE as the gNB. Preferably, in this case, thesecond link operates in a non-stand-alone mode, and the gNB may provideauxiliary information for other UEs in the first cell to access theenUE. The enUE communicates, by using a protocol stack which is usedwhen serving other UEs in the enhanced mode configured by the gNB, withother UEs in the second link, and communicates, by using its own UEprotocol stack, with the gNB in the first link. The enUE forwards dataaccording to the configuration information of the enhanced modeconfigured by the gNB. For example, if the following configuration isincluded in the configuration information: the information on a planeserved by a protocol stack used by the UE in the enhanced mode includesboth control plane data and user plane data and the data direction inthe plane by the protocol stack used by the UE in the enhanced modeincludes uplink data and downlink data, then the enUE forwards uplinkcontrol plane data and uplink user plane data from other UEs to the gNBand also forwards downlink control plane data and downlink user planedata from the gNB, which are intended for other UEs, to other UEs.

The information on a plane served by a protocol stack used in theUE-enhanced mode in the configuration information may include only oneof the control plane data and the user plane data, or the data directionin the plane served by the protocol stack used in the UE-enhanced modemay include only one of the uplink data and the downlink data. Forexample, the information on a plane served by a protocol stack used inthe UE-enhanced mode includes only the user plane data, other UEsexchange the control plane data with the gNB in other ways, for example,other UEs are directly connected to the gNB.

This configuration information may further include configurationinformation related to forwarding of data of other UEs. In addition, theconfiguration information related to forwarding of data of other UEs maybe transmitted to the UE by an RRC signaling different from the aboveRRC signaling.

Embodiment 9

This embodiment describes a case where the gNB indicates an enUE toenter an enhanced mode B3 in order to forward data of other UEs.

The gNB may select one UE, and indicate the UE to enter an enhanced modeB3 (i.e., indicate the UE to become an enUE) by using an RRC signaling(for example, RRC RECONFIGURATION) which carries configurationinformation of a UE-enhanced mode. The UE executes this operation andmay reply with an RRC signaling (for example, RRC RECONFIGURATIONCOMPLETE) to notify the gNB of the successive execution of this step.This configuration information may further include configurationinformation related to forwarding of data of other UEs. In addition, theconfiguration information related to forwarding of data of other UEs maybe transmitted to the UE by an RRC signaling different from the aboveRRC signaling.

After the UE becomes an enUE, it operates in the enhanced mode B3. Ifthe enUE forms a second cell as described above, preferably, in thiscase, the second cell operates in a non-stand-alone mode, and the gNBconfigures the second cell as the secondary cell for part or all of UEsin the first cell, and activates the second cell on the part or all ofother UEs if necessary. The gNB may activate the second cell bytransmitting an activation signaling. The first cell and the second cellmay be at a same frequency or different frequencies. The gNB shallprovide context information (for example, a user ID, information carriedby user data, information carried by a user signaling) of the part orall of UEs to the enUE. The enUE communicates with other UEs by using aprotocol stack which is used to serve other UEs in the enhanced modeconfigured by the gNB, and communicates with the gNB by using its own UEprotocol stack. The enUE forwards data according to the configurationinformation of the enhanced mode configured by the gNB. For example, ifthe following configuration is included in the configurationinformation: the information on a plane served by a protocol stack usedby the UE in the enhanced mode includes both control plane data and userplane data and the data direction in the plane by the protocol stackused by the UE in the enhanced mode includes uplink data and downlinkdata, then the enUE forwards uplink control plane data and uplink userplane data from other UEs to the gNB and also forwards downlink controlplane data and downlink user plane data from the gNB, which are intendedfor other UEs, to other UEs.

The information on a plane served by a protocol stack used in theUE-enhanced mode in the configuration information may include only oneof the control plane data and the user plane data, or the data directionin the plane served by the protocol stack used in the UE-enhanced modemay include only one of the uplink data and the downlink data. Forexample, the information on a plane served by a protocol stack used inthe UE-enhanced mode includes only the user plane data, other UEsexchange the control plane data with the gNB in other ways, for example,other UEs are directly connected to the gNB.

FIG. 20 is a schematic diagram of Embodiment 9 of the presentdisclosure. A process for processing data in the user plane and aprocess for processing data in the control plane in this embodiment willbe described in detail below with reference to FIG. 20 .

1. Processes for processing data in the user plane

(1) A process for processing downlink data between the gNB and the enUEincludes the following steps.

Step 1: The gNB processes the raw data belonging to the enUEsuccessively by the SDAP, PDCP, RLC, MAC and PHY layers, and thentransmits the data to the enUE via an interface UU1.

Step 2: The enUE processes the data received from the gNB successivelyby the PHY, MAC, RLC, PDCP and SDAP layers, to obtain the raw databelonging to the enUE.

(2) A process for processing uplink data between the gNB and the enUEincludes the following steps.

Step 1: The enUE processes the raw data successively by the SDAP, PDCP,RLC, MAC and PHY layers, and then transmits the data to the gNB via aninterface UU1.

Step 2: The gNB processes the data received from the enUE successivelyby the PHY, MAC, RLC, PDCP and SDAP layers, to obtain the raw data sentby the enUE.

(3) A process for processing downlink data between the gNB and other UEsincludes the following steps.

Step 1: The gNB processes raw data belonging to other UEs successivelyby the SDAP, PDCP, RLC, MAC and PHY layers, and then transmits the datato the enUE via an interface UU1.

Step 2: The enUE processes, according to the configuration informationrelated to forwarding of data of other UEs received by the enUE, databelonging to other UEs which is received from the gNB successively bythe PHY, MAC and RLC layers, to obtain the data belonging to other UEs.

Step 3: The enUE processes the data belonging to other UEs obtained inthe step 2 successively by the RLC, MAC and PHY layers, and thentransmits the data to corresponding other UEs via an interface UU2.

Step 4: The corresponding other UEs process the received datasuccessively by the PHY, MAC, RLC, PDCP and SDAP layers, to obtain theraw data sent to the corresponding other UEs by the gNB.

(4) A process for processing uplink data between the gNB and other UEsincludes the following steps.

Step 1: Other UEs process raw data sent to the gNB successively by theSDAP, PDCP, RLC, MAC and PHY layers, and then transmit the data to theenUE via an interface UU2.

Step 2: The enUE processes, according to the configuration informationrelated to forwarding of data of other UEs received by the enUE, thereceived data sent to the gNB by other UEs successively by the PHY, MACand RLC layers, to obtain the data sent to the gNB by other UEs.

Step 3: The enUE processes the data sent to the gNB by other UEsobtained in the step 2 successively by the RLC, MAC and PHY layers, andthen transmits the data to the gNB via an interface UU1.

Step 4: The gNB processes the received data successively by the PHY,MAC, RLC, PDCP and SDAP layers, to obtain the raw data sent to the gNBby other UEs.

During this process, the interface UU1 may perform data transmission viaa wired link, or perform data transmission via a wireless link. Theinterface UU2 performs data transmission via a wireless link.

2. Processes for processing data in the control plane

(1) A process for processing a downlink control signaling between thegNB and the enUE includes the following steps.

Step 1: The gNB generates a control signaling belonging to the enUE inan RRC layer.

Step 2: The gNB processes the control signaling belonging to the enUE,which is generated in the step 1, successively by the PDCP, RLC, MAC andPHY layers, and then transmits the control signaling to the enUE via aninterface UU1.

Step 3: The enUE processes the signaling received from the gNBsuccessively by the PHY, MAC, RLC, PDCP and RRC layers, to obtain thecontrol signaling belonging to the enUE.

(2) A process for processing an uplink control signaling between the gNBand the enUE includes the following steps.

Step 1: The enUE generates a control signaling belonging to the enUE inan RRC layer.

Step 2: The enUE processes the control signaling generated in the step 1successively by the PDCP, RLC, MAC and PHY layers, and then transmitsthe control signaling to the gNB via an interface UU1.

Step 3: The gNB processes the signaling received from the enUEsuccessively by the PHY, MAC, RLC, PDCP and RRC layers, to obtain thecontrol signaling sent by the enUE.

(3) A process for processing a downlink control signaling between thegNB and other UEs includes the following steps.

Step 1: The gNB generates a control signaling belonging to other UEs inan RRC layer.

Step 2: The gNB processes the control signaling belonging to other UEssuccessively by the PDCP, RLC, MAC and PHY layers, and then transmitsthe control signaling to the enUE via an interface UU1.

Step 3: The enUE processes, according to the configuration informationrelated to forwarding of data of other UEs received by the enUE, thesignaling belonging to other UEs which is received from the gNBsuccessively by the PHY, MAC and RLC layers, to obtain the databelonging to other UEs.

Step 4: The enUE processes the signaling belonging to other UEs obtainedin the step 3 successively by the RLC, MAC and PHY layers, and thentransmits the signaling to corresponding other UEs via an interface UU2.

Step 5: The corresponding other UEs process the received datasuccessively by the PHY, MAC, RLC, PDCP and RRC layers, to obtain thecontrol signaling sent to the corresponding other UEs by the gNB.

During this process, the control signaling belonging to other UEs maynot be forwarded to other UEs by the enUE. That is, in the step 2, thegNB processes the control signaling belonging to other UEs successivelyby the PDCP, RLC, MAC and PHY layers, and then directly transmits thecontrol signaling to other UEs by an interface UU1 or other interfaces;and then, other UEs obtain the control signaling sent to other UEs bythe gNB according to the step 5. This is just as the process in theabove description: the UE-enhanced mode serves only the user plane dataof other UEs, not the control plane data of other UEs; Alternatively,the UE-enhanced mode serves only the uplink transmission direction ofother UEs, not the downlink transmission direction of other UEs.

(4) A process for processing an uplink control signaling between the gNBand other UEs includes the following steps.

Step 1: Other UEs generate a control signaling in an RRC layer.

Step 2: Other UEs process the control signaling in the step 1successively by the PDCP, RLC, MAC and PHY layers, and then transmit thecontrol signaling to the gNB via an interface UU2.

Step 3: The enUE processes, according to the configuration informationrelated to forwarding of data of other UEs received by the enUE, thesignaling received from other UEs successively by the PHY, MAC and RLClayers, to obtain the data belonging to other UEs.

Step 4: The enUE processes the data belonging to other UEs obtained inthe step 3 successively by the RLC, MAC and PHY layers, and thentransmits the data to the gNB via an interface UU1.

Step 5: The gNB processes the received data successively by the PHY,MAC, RLC, PDCP and RRC layers, to obtain the control signaling sent byother UEs.

During this process, the control signaling may not be forwarded to thegNB by the enUE. That is, in the step 2, other UEs process the controlsignaling successively by the PDCP, RLC, MAC and PHY layers, and thendirectly transmit the control signaling to the gNB via an interface UU1or other interfaces; and then, the gNB obtains the control signalingsent by other UEs according to the step 5. This is just as the processin the above description: the UE-enhanced mode serves only the userplane data of other UEs, not the control plane data of other UEs;Alternatively, the UE-enhanced mode serves only the downlinktransmission direction of other UEs, not the uplink transmissiondirection of other UEs.

During this process, the interface UU1 may perform data transmission viaa wired link, or perform data transmission via a wireless link. Theinterface UU2 performs data transmission via a wireless link.

Embodiment 10

This embodiment describes a case where the gNB indicates an enUE toenter an enhanced mode B6 in order to forward data of other UEs.

The gNB may select one UE, and indicate the UE to enter an enhanced modeB6 (i.e., indicate the UE to become an enUE) by using an RRC signaling(for example, RRC RECONFIGURATION) which carries configurationinformation of a UE-enhanced mode. The UE executes this operation andmay reply with an RRC signaling (for example, RRC RECONFIGURATIONCOMPLETE) to notify the gNB of the successive execution of this step.This configuration information may further include configurationinformation related to forwarding of data of other UEs. In addition, theconfiguration information related to forwarding of data of other UEs maybe transmitted to the UE by an RRC signaling different from the aboveRRC signaling.

After the UE becomes an enUE, the communicates with other UEs by using aprotocol stack which is used when serving other UEs in the enhanced modeconfigured by the gNB, and communicates with the gNB by using its own UEprotocol stack. The enUE forwards data according to the configurationinformation of the enhanced mode configured by the gNB. For example, ifthe following configuration is included in the configurationinformation: the information on a plane served by a protocol stack usedby the UE in the enhanced mode includes both control plane data and userplane data and the data direction in the plane by the protocol stackused by the UE in the enhanced mode includes uplink data and downlinkdata, then the enUE forwards uplink control plane data and uplink userplane data from other UEs to the gNB and also forwards downlink controlplane data and downlink user plane data from the gNB, which are intendedfor other UEs, to other UEs.

The information on a plane served by a protocol stack used in theUE-enhanced mode in the configuration information may include only oneof the control plane data and the user plane data, or the data directionin the plane served by the protocol stack used in the UE-enhanced modemay include only one of the uplink data and the downlink data. Forexample, the information on a plane served by a protocol stack used inthe UE-enhanced mode includes only the user plane data, and other UEsexchange the control plane data with the gNB in other ways, for example,other UEs are directly connected to the gNB.

FIG. 21 is a schematic diagram of Embodiment 10 of the presentdisclosure.

1. Processes for processing data in the user plane

(1) A process for processing downlink data between the gNB and the enUEincludes the following steps.

Step 1: The gNB processes the raw data belonging to the enUEsuccessively by the SDAP, PDCP, RLC, MAC and PHY layers, and thentransmits the data to the enUE via an interface UU1.

Step 2: The enUE processes the data received from the gNB successivelyby the PHY, MAC, RLC, PDCP and SDAP layers, to obtain the raw databelonging to the enUE.

(2) A process for processing uplink data between the gNB and the enUEincludes the following steps.

Step 1: The enUE processes the raw data successively by the SDAP, PDCP,RLC, MAC and PHY layers, and then transmits the data to the gNB via aninterface UU1.

Step 2: The gNB processes the data received from the enUE successivelyby the PHY, MAC, RLC, PDCP and SDAP layers, to obtain the raw data sentby the enUE.

(3) A process for processing downlink data between the gNB and other UEsincludes the following steps.

Step 1: The gNB processes raw data belonging to other UEs successivelyby the SDAP, PDCP, RLC, MAC and PHY layers, and then transmits the datato the enUE via an interface UU1.

Step 2: The enUE processes, according to the configuration informationrelated to forwarding of data of other UEs received by the enUE, databelonging to other UEs which is received from the gNB successively bythe PHY layer and part of the MAC layer (L-MAC), to obtain the databelonging to other UEs. Among others, the L-MAC in one embodimentincludes a function having a high time delay requirement, for example,HARQ.

Step 3: The enUE processes the data belonging to other UEs obtained inthe step 2 successively by part of the MAC layer (L-MAC) and the PHYlayer, and then transmits the data to corresponding other UEs via aninterface UU2. Among others, the L-MAC in one embodiment includes afunction having a high time delay requirement, for example, HARQ.

Step 4: The corresponding other UEs process the received datasuccessively by the PHY, MAC, RLC, PDCP and SDAP layers, to obtain theraw data sent to other UEs by the gNB.

(4) A process for processing uplink data between the gNB and other UEsincludes the following steps.

Step 1: Other UEs process raw data sent to the gNB successively by theSDAP, PDCP, RLC, MAC and PHY layers, and then transmit the data to theenUE via an interface UU2.

Step 2: The enUE processes, according to the configuration informationrelated to forwarding of data of other UEs received by the enUE, thereceived data sent to the gNB by other UEs successively by the PHY layerand part of the MAC layer (L-MAC), to obtain the data sent to the gNB byother UEs. Among others, the L-MAC in one embodiment includes a functionhaving a high time delay requirement, for example, HARQ.

Step 3: The enUE processes the data sent to the gNB by other UEsobtained in the step 2 successively by part of the MAC layer (L-MAC) andthe PHY layer, and then transmits the data to the gNB via an interfaceUU. Among others, the L-MAC in one embodiment includes a function havinga high time delay requirement, for example, HARQ.

Step 4: The gNB processes the received data successively by the PHY,MAC, RLC, PDCP and SDAP layers, to obtain the raw data sent to the gNBby UEs.

During this process, the interface UU1 may perform data transmission viaa wired link, or perform data transmission via a wireless link. Theinterface UU2 performs data transmission via a wireless link.

2. Processes for processing data in the control plane

(1) A process for processing a downlink control signaling between thegNB and the enUE includes the following steps.

Step 1: The gNB generates a control signaling belonging to the enUE inan RRC layer.

Step 2: The gNB processes the control signaling belonging to the enUE,which is generated in the step 1, successively by the PDCP, RLC, MAC andPHY layers, and then transmits the control signaling to the enUE via aninterface UU1.

Step 3: The enUE processes the signaling received from the gNBsuccessively by the PHY, MAC, RLC, PDCP and RRC layers, to obtain thecontrol signaling belonging to the enUE.

(2) A process for processing an uplink control signaling between the gNBand the enUE includes the following steps.

Step 1: The enUE generates a control signaling belonging to the enUE inan RRC layer.

Step 2: The enUE processes the control signaling generated in the step 1successively by the PDCP, RLC, MAC and PHY layers, and then transmitsthe control signaling to the gNB via an interface UU1.

Step 3: The gNB processes the signaling received from the enUEsuccessively by the PHY, MAC, RLC, PDCP and RRC layers, to obtain thecontrol signaling sent by the enUE.

(3) A process for processing a downlink control signaling between thegNB and other UEs includes the following steps.

Step 1: The gNB generates a control signaling belonging to other UEs inan RRC layer.

Step 2: The gNB processes the control signaling belonging to other UEssuccessively by the PDCP, RLC, MAC and PHY layers, and then transmitsthe control signaling to the enUE via an interface UU1.

Step 3: The enUE processes, according to the configuration informationrelated to forwarding of data of other UEs received by the enUE, thesignaling belonging to other UEs which is received from the gNBsuccessively by the PHY layer and part of the MAC layer (L-MAC), toobtain the data belonging to other UEs. Among others, the L-MAC in oneembodiment includes a function having a high time delay requirement, forexample, HARQ.

Step 4: The enUE processes the signaling belonging to other UEs obtainedin the step 3 successively by part of the MAC layer (L-MAC) and the PHYlayer, and then transmits the signaling to corresponding other UEs viaan interface UU2. Among others, the L-MAC in one embodiment includes afunction having a high time delay requirement, for example, HARQ.

Step 5: The corresponding other UEs process the received signalingsuccessively by the PHY, MAC, RLC, PDCP and RRC layers, to obtain thecontrol signaling sent to the corresponding other UEs by the gNB.

During this process, the control signaling belonging to other UEs maynot be forwarded to other UEs by the enUE. That is, in the step 2, thegNB processes the control signaling belonging to other UEs successivelyby the PDCP, RLC, MAC and PHY layers, and then directly transmits thecontrol signaling to other UEs by an interface UU1 or other interfaces;and then, other UEs obtain the control signaling sent to other UEs bythe gNB according to the step 5. This is just as the process in theabove description: the UE-enhanced mode serves only the user plane dataof other UEs, not the control plane data of other UEs; Alternatively,the UE-enhanced mode serves only the uplink transmission direction ofother UEs, not the downlink transmission direction of other UEs.

(4) A process for processing an uplink control signaling between the gNBand other UEs includes the following steps.

Step 1: Other UEs generate a control signaling in an RRC layer.

Step 2: Other UEs process the control signaling in the step 1successively by the PDCP, RLC, MAC and PHY layers, and then transmit thecontrol signaling to the gNB via an interface UU2.

Step 3: The enUE processes, according to the configuration informationrelated to forwarding of data of other UEs received by the enUE, thesignaling received from other UEs successively by the PHY layer and partof the MAC layer (L-MAC), to obtain the signaling belonging to otherUEs.

Step 4: The enUE processes the signaling belonging to other UEs obtainedin the step 3 successively by part of the MAC layer (L-MAC) and the PHYlayer, and then transmits the signaling to the gNB via an interface UU1.

Step 5: The gNB processes the received signaling successively by thePHY, MAC, RLC, PDCP and RRC layers, to obtain the control signaling sentby other UEs.

During this process, the control signaling may not be forwarded to thegNB by the enUE. That is, in the step 2, other UEs process the controlsignaling successively by the PDCP, RLC, MAC and PHY layers, and thendirectly transmit the control signaling to the gNB via an interface UU1or other interfaces; and then, the gNB obtains the control signalingsent by other UEs according to the step 5. This is just as the processin the above description: the UE-enhanced mode serves only the userplane data of other UEs, not the control plane data of other UEs;Alternatively, the UE-enhanced mode serves only the downlinktransmission direction of other UEs, not the uplink transmissiondirection of other UEs.

During this process, the interface UU1 may perform data transmission viaa wired link, or perform data transmission via a wireless link. Theinterface UU2 performs data transmission via a wireless link.

The above embodiments 1 to 4 describe data transmission in the userplane and the control plane respectively in cases where the enUEconfigures protocol stack structures B0, B3 and B6. For a case where theenUE configures other protocol stack structures, the data transmissionmethod is similar, which will not be repeated here, except that theprotocol stack structure used for processing data of other UEs needs tobe processed according to the protocol stack structure used when servingother UEs in the enhanced mode configured by the gNB.

Embodiment 11

This embodiment describes a case where the gNB indicates an enUE toenter an enhanced mode B6 and acquire scheduling information of the gNBin order to forward data of other UEs. FIG. 22 is a schematic diagram ofEmbodiment 11 of the present disclosure, including the following steps.

Step 2201: The gNB selects one UE, and transmits configurationinformation that indicates the UE to enter an enhanced mode (i.e.,indicates the UE to become an enUE) by using an RRC signaling (forexample, RRC RECONFIGURATION). This configuration information mayfurther include configuration information related to forwarding of dataof other UEs. In addition, the configuration information related toforwarding of data of other UEs may be transmitted to the UE by an RRCsignaling different from the above RRC signaling. The UE executes thisoperation and replies with an RRC signaling (for example, RRCRECONFIGURATION COMPLETE) to notify the gNB of the successive executionof this step.

For downlink transmission:

Step 2202: The frequency information used by the first link (in thisembodiment, the definition of the first link and the second link is thesame as that in Embodiment 7) is called a frequency band 1, and the gNBtransmits, to the enUE, user plane data intended for other UEs on thefrequency band 1.

Step 2203: The frequency information used between the gNB and other UEsis called a frequency band 2, and the gNB transmits the schedulinginformation to other UEs on the frequency band 2. Meanwhile, the enUEacquires the scheduling information from the gNB. Time-frequencyresources that may be used for transmitting the user plane data arespecified in the scheduling information.

Step 2204: The frequency information used by the second link is called afrequency band 3, and the frequency band 3 and the frequency band 2 maybe at a same frequency or different frequencies. The enUE transmits thedownlink data to other UEs on the frequency band 3 according to thescheduling information from the gNB.

For uplink transmission:

Step 2205: The gNB transmits the scheduling information to other UEs onthe frequency band 2. Meanwhile, the enUE acquires the schedulinginformation from the gNB. Time-frequency resources that may be used fortransmitting the user plane data are specified in the schedulinginformation.

Step 2206: The enUE receives the uplink data from other UEs on thefrequency band 3 according to the scheduling information from the gNB.The frequency band 3 and the frequency band 2 may be at a same frequencyor different frequencies.

Step 2207: The enUE forwards, on the frequency band 1, the uplink datafrom other UEs to the gNB.

Correspondingly to the method, the present disclosure further provides adata forwarding UE, including:

a mode switching module configured to enter an enhanced mode accordingto an indication received from a base station; and

a data forwarding module configured to forward data between a basestation and a second UE.

According to one embodiment of the present invention, the equipment mayfurther include a module configured to receive, from the base station,scheduling information on time-frequency resources of the second UE.

In this case, the data forwarding module is configured to forward databetween the base station and the second UE in the following way:receiving downlink data sent to a second UE from a base station,processing the downlink data layer by layer by a protocol stackstructure corresponding to the equipment in the enhanced mode, andforwarding, to the corresponding second UE, the downlink data on thecorresponding time-frequency resources according to the schedulinginformation on the time-frequency resources of the second UE; and/orreceiving uplink data sent to a base station from a second UE oncorresponding time-frequency resources according to the schedulinginformation on the time-frequency resources of the second UE, processingthe uplink data layer by layer by a protocol stack structurecorresponding to the equipment in the enhanced mode, and forwarding theuplink data to the base station.

According to another embodiment of the present invention, the equipmentmay further include a module configured to transmit, to the second UE,the scheduling information on the time-frequency resources.

In this case, the data forwarding module is configured to forward databetween the base station and the second UE in the following way:receiving downlink data sent to a second UE from a base station,processing the downlink data layer by layer by a protocol stackstructure corresponding to the equipment in the enhanced mode, andforwarding, to the corresponding second UE, the downlink data on thecorresponding time-frequency resources according to the schedulinginformation; and/or receiving uplink data sent to a base station from asecond UE on corresponding time-frequency resources according to thescheduling information, processing the uplink data layer by layer by aprotocol stack structure corresponding to the equipment in the enhancedmode, and forwarding the uplink data to the base station.

Preferably, the equipment may further include: a module configured toreceive access information and cell configuration information from thebase station, the access information is used by a second UE to accessthe UE: and

a module configured to transmit the access information and the cellconfiguration information to the second UE and accept an access requestfrom the second UE.

Preferably, the equipment may further include a module configured toreport channel state information of a first link to the base station,the first link being a link between the UE and the base station. Thechannel state information is used by the base station to select a firstUE having a channel condition better than a first set threshold to enterthe enhanced mode in order to forward data between a second UE having achannel condition worse than a second set threshold and the basestation.

Preferably, the equipment may further include a module configured toreport, to the base station, channel state information on at least onecarriers between the UE and the second UE on at least one carrier.

Preferably, the equipment further includes a report module configured toreport, to the base station, a protocol stack structure informationsupported by the UE in the enhanced mode. The protocol stack structuresupported by the equipment in the enhanced mode at least includes one ofthe following structures:

protocol stack structure B0, including: a Radio Resource Control (RRC)layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio LinkControl (RLC) layer, a Media Access Control (MAC) layer and a physical(PHY) layer in the control plane, and a Service Data Adaptation Protocol(SDAP) layer, a PDCP layer, an RLC layer, an MAC layer and a PHY layerin the user plane;

protocol stack structure B1, including: a PDCP layer, an RLC layer, anMAC layer and a PHY layer;

protocol stack structure B2, including: part of a PDCP layer, an RLClayer, an MAC layer and a PHY layer;

protocol stack structure B3, including: an RLC layer, an MAC layer and aPHY layer;

protocol stack structure B4, including: part of an RLC layer, an MAClayer and a PHY layer;

protocol stack structure B5, including: an MAC layer and a PHY layer;

protocol stack structure B6, including: part of an MAC layer and a PHYlayer;

protocol stack structure B7, including: a PHY layer; and

protocol stack structure B8, including: part of a PHY layer.

Preferably, the indication from the base station includes at least oneof the following information:

a. a protocol stack structure information used by a first UE in anenhanced mode;

b. information on a plane that the protocol stack structure informationserves;

c. a data transmission direction information of a plane that theprotocol stack structure information serves; and

d. ID information of a second UE that the first UE serves.

Preferably, information on the indication from the base station mayinclude following combinations:

only a configured;

only a set of a and b configured, or at least two different sets of aand b configured;

only a set of a and c configured, or at least two different sets of aand c configured;

only a set of a and d configured, or at least two different sets of aand d configured;

only a set of a, b and c configured, or at least two different sets ofa, b and c configured;

only a set of a, b and d configured, or at least two different sets ofa, b and d configured;

only a set of a, c and d configured, or at least two different sets ofa, c and d configured; and

only a set of a, b, c and d configured, or at least two different setsof a, b, c and d configured.

Preferably, the indication from the base station includes at least oneof the following information: a duplex mode used by a second link, acarrier and a bandwidth used by a second link, a physical cell ID of acell where a second link is located, a maximum transmission power of afirst UE in the enhanced mode in a second link, and an operating mode ofa second link; and

Among them, the second link is a link between a first UE in the enhancedmode and a second UE.

Preferably, before forwarding, by the UE, data between the base stationand a second UE, the UE further receives, from a base station,configuration information related to forwarding of data of a second UE,the configuration information being used to indicate data to beforwarded.

The configuration information related to forwarding of data of a secondUE at least includes one of the following information:

ID information of a second UE to which the data to be forwarded belongs;

indication information of a bearer to which the data to be forwardedbelongs;

ID information of a logical channel to which the data to be forwardedbelongs; and

information on physical resources to which the data to be forwardedbelongs.

Correspondingly to the method on the UE side, the present disclosurefurther provides a data forwarding method on the base station side,including:

transmitting, to a first UE having the capability of supporting anenhanced mode, an indication to enter the enhanced mode; and

forwarding data with a second UE by the first UE.

Preferably, the method may further include: transmitting, to the firstUE, scheduling information on time-frequency resources of the second UEscheduled by a base station.

Preferably, the method may further include: transmitting, to the firstUE, cell configuration information and access information used by asecond UE to access the first UE; or transmitting, to a second UE,access information used by the second UE to access the first UE.

Preferably, the method may further include: receiving channel stateinformation of a first link reported by the first UE. Preferably, thetransmitting, to a first UE having the capability of supporting anenhanced mode, an indication to enter the enhanced mode includes:selecting, according to channel state information of a first linkreported by each UE, a first UE having a channel condition better than afirst set threshold, and transmitting, to the first UE having thechannel condition better than the first set threshold, an indication toenter an enhanced mode in order to forward data between a second UEhaving a channel condition worse than a second set threshold and a basestation.

Preferably, the indication from the base station includes at least oneof the following information:

a. a protocol stack structure information used by a first UE in anenhanced mode;

b. information on a plane that the protocol stack structure informationserves;

c. a data transmission direction information of a plane that theprotocol stack structure information serves; and

d. ID information of a second UE that the first UE serves.

Preferably, the method may further include: transmitting, by a basestation and to a first UE, configuration information related toforwarding of data of a second UE, the configuration information beingused to indicate data to be forwarded.

Preferably, the configuration information related to forwarding of dataof a second UE at least includes one of the following information:

ID information of a second UE to which the data to be forwarded belongs;

indication information of a bearer to which the data to be forwardedbelongs;

ID information of a logical channel to which the data to be forwardedbelongs; and

information on physical resources to which the data to be forwardedbelongs.

Correspondingly to the method on the access node side, the presentdisclosure further provides a base station, including:

an indicating module configured to transmit, to a first UE having thecapability of supporting an enhanced mode, an indication to enter theenhanced mode; and

a forward processing module configured to forward data of a second UE bythe first UE.

Preferably, the method may further include: transmitting, to the firstUE, scheduling information on time-frequency resources of the second UEscheduled by a base station.

Preferably, the equipment may further include: a module configured totransmit, to the first UE, cell configuration information and accessinformation used by a second UE to access the first UE; or a moduleconfigured to transmit, to a second UE, access information used by thesecond UE to access the first UE.

Preferably, the equipment may further include a module configured toreceive channel state information of a first link reported by the firstUE. Preferably, the transmitting, to a first UE having the capability ofsupporting an enhanced mode, an indication to enter the enhanced modeincludes: selecting, according to channel state information of a firstlink reported by each UE, a first UE having a channel condition betterthan a first set threshold, and transmitting, to the first UE having thechannel condition better than the first set threshold, an indication toenter an enhanced mode in order to forward data between a second UEhaving a channel condition worse than a second set threshold and a basestation.

Preferably, the indication from the base station includes at least oneof the following information:

a. a protocol stack structure information used by a first UE in anenhanced mode;

b. information on a plane that the protocol stack structure informationserves;

c. a data transmission direction information of a plane that theprotocol stack structure information serves; and

d. ID information of a second UE that the first UE serves.

Preferably, the base station may also transmit, to a first UE,configuration information related to forwarding of data of a second UE,the configuration information being used to indicate data to beforwarded.

The configuration information related to forwarding of data of a secondUE at least includes one of the following information:

ID information of a second UE to which the data to be forwarded belongs;

indication information of a bearer to which the data to be forwardedbelongs;

ID information of a logical channel to which the data to be forwardedbelongs; and

information on physical resources to which the data to be forwardedbelongs.

FIG. 23 illustrates a block diagram detailing an internal structure of aterminal according to an embodiment of the present disclosure. Asillustrated in FIG. 23 , the terminal of the present disclosure mayinclude a terminal processor 2301, a receiver 2302, and a transmitter2303.

The terminal processor 2301 may control a process to operate theterminal according to embodiments of the present disclosure as describedabove. For example, the terminal operation can be controlled differentlyaccording to different numerologies according to embodiments of thepresent disclosure.

The terminal receiver 2302 and the terminal transmitter 2303 may becollectively referred to as a transceiver. The transceiver maytransmit/receive a signal to/from the base station and/or otherterminals. To this end, the transceiver may include an RF transmitterthat up-converts and amplifies a frequency of the transmitted signal, anRF receiver that low-noise-amplifies the received signal anddown-converts the frequency, or the like. Further, the transceiver mayreceive a signal through a radio channel and output the received signalto the terminal processor 2301 and transmit the signal output from theterminal processor 2301 through the radio channel.

FIG. 24 illustrates a block diagram of an internal structure of the basestation according to embodiments of the present disclosure. Asillustrated in FIG. 24 , the base station of the present disclosure mayinclude a base station processor 2401, a receiver 2402, and atransmitter 2403. The structure of the base station illustrated in FIG.24 may be applied to above described CU and/or DU.

The base station processor 2401 may control a process to operate thebase station according to some embodiments of the present disclosure asdescribed herein. For example, the base station operation can becontrolled differently according to different numerologies.

The base station receiver 2402 and the base station transmitter 2403 arecollectively referred to as a transceiver. The transceiver maytransmit/receive a signal to/from the terminal. To this end, thetransceiver may include an RF transmitter that up-converts and amplifiesa frequency of the transmitted signal, an RF receiver thatlow-noise-amplifies the received signal and down-converts the frequency,or the like. Further, the transceiver may receive a signal through aradio channel and output the received signal to the base stationprocessor 2401 and transmit the signal output from the base stationprocessor 2401 through the radio channel.

What is described in the foregoing are only embodiments of the presentdisclosure, and should not be construed as limitations to the presentdisclosure. Any changes, equivalent replacements, modifications madewithout departing from the scope and spirit of the present disclosureare intended to be included within the protecting scope of the presentdisclosure.

What is claimed:
 1. A method performed by a central unit (CU) of agNodeB (gNB) including the CU and a plurality of distributed units(DUs), the method comprising: receiving a first message including ameasurement report associated with a terminal; transmitting, to a targetDU of the NB, a second message for establishing a context associatedwith the terminal in the target DU, based on the first message, thesecond message including a first identifier allocated for the terminalby the CU; receiving, from the target DU of gNB, a third message as aresponse to the second message, the third message including the firstidentifier allocated for the terminal by the CU and a second identifierallocated for the terminal by the target DU; transmitting, to a sourceDU of the gNB, a fourth message including a radio resource control (RRC)reconfiguration message and information for stopping data transmissionassociated with the terminal; and transmitting, to the source DU of thegNB, a fifth message for releasing a context associated with theterminal in the source DU of the gNB.
 2. The method of claim 1, whereinthe first message is received from the source DU of the gNB.
 3. Themethod of claim 1, wherein the third message further includes a cellradio network temporary identifier (C-RNTI) allocated for the terminalby the target DU of the gNB.
 4. The method of claim 1, wherein thesecond message further includes at least one of information associatedwith a signal radio bearer (SRB) to be configured by the target DU ofthe gNB or information associated with a data radio bearer (DRB) to beconfigured by the target DU of the gNB, and wherein the third messagefurther includes at least one of information associated with the SRBconfigured by the target DU of the gNB or information associated the DRBconfigured by the target DU of the gNB.
 5. The method of claim 1,wherein the second message further includes terminal radio capabilityinformation.
 6. The method of claim 1, further comprising: receiving,from the source DU of the gNB, a sixth message associated with a datatransfer status based on the fourth message, the sixth message includingat least one of first information on a sequence number of data that hasbeen transmitted successfully or second information on a sequence numberof data that has not been transmitted successfully.
 7. The method ofclaim 6, wherein data to be transmitted to the target DU is identifiedbased on the sixth message.
 8. The method of claim 1, wherein the CU hasa packet data convergence protocol (PDCP) function and an RRC function,and wherein the source DU or the target DU has a physical layerfunction, a media access control (MAC) function and a radio link control(RLC) function.
 9. A central unit (CU) of a gNodeB (gNB) including theCU and a plurality of distributed units (DUs), the CU comprising: atransceiver; and a controller coupled with the transceiver andconfigured to: receive, a first message including a measurement reportassociated with a terminal, transmit, to a target DU of the gNB, asecond message for establishing a context associated with the terminalin the target DU, based on the first message, the second messageincluding a first identifier allocated for the terminal by the CU,receive, from the target DU of the gNB, a third message as a response tothe second message, the third message including the first identifierallocated for the terminal by the CU and a second identifier allocatedfor the terminal by the target DU, transmit, to a source DU of the gNB,a fourth message including a radio resource control (RRC)reconfiguration message and information for stopping data transmissionassociated with the terminal, and transmit, to the source DU of the gNB,a fifth message for releasing a context associated with the terminal inthe source DU of the gNB.
 10. The CU of claim 9, wherein the firstmessage is received from the source DU of the gNB.
 11. The CU of claim9, wherein the third message further includes a cell radio networktemporary identifier (C-RNTI) allocated for the terminal by the targetDU of the gNB.
 12. The CU of claim 9, wherein the second message furtherincludes at least one of information associated with a signal radiobearer (SRB) to be configured by the target DU of the gNB or informationassociated with a data radio bearer (DRB) to be configured by the targetDU of the gNB, and wherein the third message further includes at leastone of information associated with the SRB configured by the target DUof the gNB or information associated the DRB configured by the target DUof the gNB.
 13. The CU of claim 9, wherein the second message furtherincludes terminal radio capability information.
 14. The CU of claim 9,wherein the controller is further configured to receive, from the sourceDU of the gNB, a sixth message associated with a data transfer statusbased on the fourth message, the sixth message including at least one offirst information on a sequence number of data that has been transmittedsuccessfully or second information on a sequence number of data that hasnot been transmitted successfully.
 15. The CU of claim 14, wherein datato be transmitted to the target DU is identified based on the sixthmessage.
 16. The CU of claim 9, wherein the CU has a packet dataconvergence protocol (PDCP) function and an RRC function, and whereinthe source DU or the target DU has a physical layer function, a mediaaccess control (MAC) function and a radio link control (RLC) function.17. A method performed by a source distributed unit (DU) of a gNodeB(gNB) including a central unit (CU) and a plurality of DUs, the methodcomprising: receiving, from a terminal, a measurement report;transmitting, to the CU of the gNB, a first message including themeasurement report associated with the terminal; receiving, from the CUof the gNB, a second message including a radio resource control (RRC)reconfiguration message and information for stopping data transmissionassociated with the terminal; transmitting, to the terminal, the RRCreconfiguration message included in the second message; receiving, fromthe CU of the gNB, a third message for releasing a context associatedwith the terminal in the source DU of the gNB; and releasing the contextassociated with the terminal in the source DU of the gNB, based on thethird message, wherein the data transmission associated with theterminal is stopped based on the information.
 18. The method of claim17, further comprising: transmitting, to the CU of the gNB, a fourthmessage associated with a data transfer status based on the secondmessage, the fourth message including at least one of first informationon a sequence number of data that has been transmitted successfully orsecond information on a sequence number of data that has not beentransmitted successfully.
 19. The method of claim 17, wherein the CU hasa packet data convergence protocol (PDCP) function and an RRC function,and wherein the source DU has a physical layer function, a media accesscontrol (MAC) function and a radio link control (RLC) function.
 20. Asource distributed unit (DU) of a gNodeB (gNB) including a central unit(CU) and a plurality of DUs, the source DU comprising: a transceiver;and a controller coupled with the transceiver and configured to:receive, from a terminal, a measurement report, transmit, to a centralunit (CU) of the gNB, a first message including the measurement reportassociated with the terminal, receive, from the CU of the gNB, a secondmessage including a radio resource control (RRC) reconfiguration messageand information for stopping data transmission associated with theterminal, transmit, to the terminal, the RRC reconfiguration messageincluded in the second message, receive, from the CU of the gNB, a thirdmessage for releasing a context associated with the terminal in thesource DU of the gNB, and release the context associated with theterminal in the source DU of the gNB, based on the third message,wherein the data transmission associated with the terminal is stoppedbased on the information.
 21. The source DU of claim 20, wherein thecontroller is further configured to transmit, to the CU of the gNB, afourth message associated with a data transfer status based on thesecond message, the fourth message including at least one of firstinformation on a sequence number of data that has been transmittedsuccessfully or second information on a sequence number of data that hasnot been transmitted successfully.
 22. The source DU of claim 20,wherein the CU has a packet data convergence protocol (PDCP) functionand an RRC function, and wherein the source DU has a physical layerfunction, a media access control (MAC) function and a radio link control(RLC) function.
 23. A method performed by a target distributed unit (DU)of a gNodeB (gNB) including a central unit (CU) and a plurality of DUs,the method comprising: receiving, from the CU of the gNB, a firstmessage for establishing a context associated with a terminal, the firstmessage including a first identifier allocated for the terminal by theCU; transmitting, to the CU of the gNB, a second message as a responseto the first message, the second message including the first identifierallocated for the terminal by the CU and a second identifier allocatedfor the terminal by the target DU; receiving, from the terminal, a radioresource control (RRC) message associated with the terminal; andtransmitting, to the CU of the gNB, a third message including the RRCmessage, wherein at least one of a signaling radio bearer (SRB) or adata radio bearer (DRB) for the terminal is configured based on thefirst message.
 24. The method of claim 23, wherein the second messagefurther includes a cell radio network temporary identifier (C-RNTI)allocated for the terminal by the target DU of the gNB.
 25. The methodof claim 23, wherein the first message further includes at least one ofinformation associated with a SRB to be configured by the target DU ofthe gNB or information associated with a DRB to be configured by thetarget DU of the gNB, and wherein the second message further includes atleast one of information associated with the SRB configured by thetarget DU or information associated the DRB configured by the target DU.26. The method of claim 23, wherein the first message further includesterminal radio capability information.
 27. The method of claim 23,wherein the CU has a packet data convergence protocol (PDCP) functionand an RRC function, and wherein the target DU has a physical layerfunction, a media access control (MAC) function and a radio link control(RLC) function.
 28. A target distributed unit (DU) of a gNodeB (gNB)including a central unit (CU) and a plurality of DUs, the target DUcomprising: a transceiver; and a controller coupled with the transceiverand configured to: receive, from the CU of the gNB, a first message forestablishing a context associated with a terminal, the first messageincluding a first identifier allocated for the terminal by the CU,transmit, to the CU of the gNB, a second message as a response to thefirst message, the second message including the first identifierallocated for the terminal by the CU and a second identifier allocatedfor the terminal by the target DU, receive, from the terminal, a radioresource control (RRC) message associated with the terminal, andtransmit, to the CU of the gNB, a third message including the RRCmessage, wherein at least one of a signaling radio bearer (SRB) or adata radio bearer (DRB) for the terminal is configured based on thefirst message.
 29. The target DU of claim 28, wherein the second messagefurther includes a cell radio network temporary identifier (C-RNTI)allocated for the terminal by the target DU of the gNB.
 30. The targetDU of claim 28, wherein the first message further includes at least oneof information associated with a SRB to be configured by the target DUof the gNB or information associated with a DRB to be configured by thetarget DU of the gNB, and wherein the second message further includes atleast one of information associated with the SRB configured by thetarget DU or information associated the DRB configured by the target DU.31. The target DU claim 28, wherein the first message further includesterminal radio capability information.
 32. The target DU of claim 28,wherein the CU has a packet data convergence protocol (PDCP) functionand an RRC function, and wherein the target DU has a physical layerfunction, a media access control (MAC) function and a radio link control(RLC) function.